Auswahl der wissenschaftlichen Literatur zum Thema „Syndrome de Shwachman-Diamond“

Shwachman–Diamond syndrome is a rare genetic disorder with an autosomal recessive inheritance pattern. Most often (in more than 90% of cases) this disease is caused by biallelic pathogenic variants in the highly conserved SBDS gene located on the long arm of chromosome 7. However, approximately 10% of patients with the clinical phenotype of Shwachman–Diamond syndrome lack mutations in SBDS but have pathogenic variants in other genes, such as DNAJC21 or EFL1. Shwachman–Diamond syndrome is a multisystemic disorder characterized by exocrine pancreatic insufficiency, protein-energy undernutrition, delayed physical development, cognitive disorders, anomalies of the skeletal system, and immunological disorders. In addition to the described symptoms, Shwachman–Diamond syndrome is characterized by the presence of bone marrow failure (most often neutropenia and anemia), as well as an increased risk of cytogenetic abnormalities and a predisposition to myelodysplastic syndromes and acute myeloid leukemia. In this review, the authors summarize the spectrum of hematological disorders observed in Shwachman–Diamond syndrome, as well as describe the molecular mechanisms underlying them.

This article describes a clinical case of a rare Schwachman–Diamond syndrome. It covers the features of the clinical picture of the disease and the laboratory examinations. A multidisciplinary approach for the purpose of early diagnosis, timely initiation of complex treatment, including nutritional therapy, prescription of enzyme preparations and granulocyte colony-stimulating factor, makes it possible to improve the quality of life and prognosis in such patients.

Shwachman-Diamond syndrome (SDS) is a rare autosomal recessive disorder with an incidence of 1 in 50.000 births. In 2001, the genetic defect of SDS was mapped to the centromeric region of chromosome 7 and in 2003 the defect was narrowed down to a single gene, which was named the Shwachman-Bodian-Diamond Syndrome (SBDS) gene. The mutations in the SBDS gene were identified in 90% of patients. Pancreatic exocrine insufficiency, bone marrow dysfunction with peripheral blood cytopenias, skeletal abnormalities, short stature and immune dysfunction characterize the disorder. Neutropenia plays a crucial role in the occurrence of recurrent and severe infectious complications representing one of the major causes of death in SDS patients. The aim of our study is to better comprehend the marrow dysfunction occurring in SDS patients, by analysing the functional properties of bone marrow (BM)-derived mesenchymal stem cells (MSCs). BM cells obtained from patients and healthy donors (HDs) were plated in sterile tissue culture flasks. At the third passage of the culture, cells were tested for the expression of specific surface markers, their ability to differentiate into mesengenic lineages, their capability to abrogate T cell proliferation and their ability to prevent neutrophil apoptosis. MSCs derived from SDS patients (SDS-MSCs) displayed typical fibroblastoid morphology; they were consistently devoid of contaminating hematopoietic cells, being negative for CD34, CD45, HLA-DR, CD11b, CD19, and CD14, but expressed common MSC markers including CD90, CD73, CD105 and HLA-ABC. Similarly to MSCs obtained from healthy donors (HD-MSCs), these cells were able to differentiate into adipocytes, osteoblasts and chondrocytes. In addition, SDS-MSCs drastically decreased the mitogen-induced lymphocyte proliferation, in a dose dependent manner. We also cultured neutrophils obtained from HD in presence or absence of MSCs at different time points. We demonstrated that SDS-MSCs were comparable to HD-MSCs in supporting the viability of neutrophils. More importantly, SDS-MSC were able to produce high amount of IL-6, a crucial cytokine involved in the protection of neutrophils from apoptosis. In addition, a genome wide gene expression analysis was carried out using HG-U133 Plus 2.0 Arrays. Results showed a SDS-MSCs specific profile, significantly different from HD-MSCs. All the genes, differentially expressed in mesenchymal cells obtained from Shwachman patients, are involved in the embryogenesis and in the development of different organs. In conclusion, we successfully isolated and characterized MSCs from 27 SDS patients. Further studies are needed to better comprehend the functional and molecular features of SDS-MSCs, which are potentially involved in the hematological abnormalities typical of SDS patients.

La Sindrome di Shwachman (SDS) è una rara malattia genetica, autosomica recessiva, caratterizzata da insufficienza pancreatica, disfunzioni ematologiche, displasie scheletriche e disordini cognitivi. Nel 90% dei pazienti vengono riscontrate mutazioni a carico del gene SBDS. Similarmente ad altre sindromi midollari, i pazienti affetti da SDS hanno un aumentato rischio di insorgenza di mielodisplasie e leucemia, ma i meccanismi responsabili di questa predisposizione non sono ancora stati indagati in modo approfondito. Le cellule mesenchimali stromali (MSCs) vengono considerate fattori con un ruolo fondamentale nel mantenere e sostenere la plasticità e la sopravvivenza delle cellule staminali all’interno della nicchia midollare. Studi recenti hanno dimostrato inoltre come mutazioni specifiche a livello delle MSCs possono essere fattori sufficienti per disregolare i sottili equilibri omeostatici all’interno della nicchia e dare inizio ad un processo di trasformazione neoplastica. Il nostro gruppo ha dimostrato che MSCs derivate da pazienti affetti da SDS erano comparabili a quelli di donatori sani per quanto riguarda le loro caratteristiche in vitro (marcatori di superficie, capacità di differenziare in diversi lineages, abilità nel sostenere la vitalità di cellule CD34). La gene expression analysis condotta su 16 SDS-MSCs in realtà mostra come queste cellule avessero un pattern di espressione genica differente da quello delle mesenchimali di donatori sani, suggerendo come le mesenchimali SDS potessero avere un ruolo nei disordini ematologici riscontrati nella malattia. In questo studio abbiamo aumentato la corte di pazienti e, avvalendoci di un modello in vivo, abbiamo studiato il possibile coinvolgimento delle MSCs nei disordini ematopoietici. Il nostro modello prevedeva l’impianto sottocutaneo in topi immunocompromessi di pellet cartilaginei derivanti da MSCs da donatori sani e pazienti stimolate per 21 giorni con un particolare medium di differenziamento. Dopo 60 giorni, gli animali sono stati sacrificati e gli ossicoli recuperati per l’analisi istologica. Dai nostri dati emerge come, al termine del periodo sperimentale, solo i pellet derivati da MSCs di donatore sano siano stati in grado di formare una nicchia midollare completa, con presenza di trabecole ossee, adipociti e cellule ematopoietiche murine. Di contro, nessuno dei pellet derivati da paziente è stato ritrovato vascolarizzato o colonizzato da cellule ematopoietiche. L’analisi a time point precoci ci ha permesso di individuare dei difetti nel processo differenziativo dei pellet derivati da pazienti, che non mostravano riassorbimento cartilagineo, né deposizione di matrice ossea o processi di vascolarizzazione. Questo dato ci suggerisce come nel nostro modello le mesenchimali da paziente mostrino difetti nel loro processo differenziativo e di conseguenza possano essere coinvolte anche nei disordini ematologici a carico del midollo. Nella seconda parte del nostro studio abbiamo testato un farmaco su cellule ematologiche e non ematologiche di paziente. Questo farmaco agisce sulle nonsense stop codon mutation, una delle mutazioni più diffuse nei pazienti SDS a carico del gene SBDS, consentendo il read-through della mutazione non senso e quindi la produzione di una proteina completa. I nostri risultati hanno mostrato l’azione positiva di questo farmaco in diverse linee cellulari (linfoblastoidi, mesenchimali e mononucleate da midollo), restorando la produzione della proteina. Inoltre, il trattamento con questo farmaco ha anche prodotto miglioramenti a livello funzionale nelle cellule mononucleate. In particolare queste cellule, in seguito al trattamento, hanno mostrato un significativo aumento nella capacità di dare colonie CFU-GM. Questo risultato ha forti conseguenze a livello clinico poiché, non avendo mostrato effetti tossici, questo farmaco potrebbe essere proposto per la cura dei disordini ematologici in questi pazienti.
Shwachman-Diamond Syndrome (SDS) is a rare autosomal recessive disease, characterized by exocrine pancreatic disorder, hematological aberrancies, bone marrow failure and cognitive impairment. In 90% of patients the SBDS gene is found mutated. Similar to other marrow failure syndromes, SDS patients have an increased risk for developing myelodysplastic syndrome and AML. To date, the mechanisms underlying the bone marrow failure in SDS patients are not fully understood. Microenvironment constituents and in particular mesenchymal stromal cells (MSCs) are considered the pivotal organizers for the generation, maintenance and plasticity of the hematopoietic stem cell niche. Recent studies show that specific changes in MSCs may be sufficient to initiate a complex phenotype of disordered homeostasis with similarities to myelodysplasia. We have demonstrated that MSCs obtained from SDS patients were comparable in vitro to HD but gene expression analysis of 16 SDS-MSCs showed that these cells had a specific gene expression signature compared to HD. These results suggest that it is possible that MSCs could be involved in the pathogenesis of the SDS marrow disorders. We increased our patients cohort and investigated whether SDS-MSCs were able to sustain malignant evolution using an innovative scaffold-free in vivo system based on the ex vivo generation of semi-cartilaginous pellets (SCPs) from human MSCs. We obtained SCPs stimulating MSCs for 21 days with a specific differentiating medium and a complete and correct formation of cartilaginous tissues both in HD and SDS samples. These SCPs were transplanted heterotopically into subcutaneous tissue of immunocompromised mice. After 60 days, we sacrificed mice and collected ossicles. We found that in 90% of cases, HD were able to recreate the hematopoietic microenvironment, with the establishment of a complete marrow niche, while none of the transplanted SDS-SCPs was able to recreate the hematopoietic microenvironment, revealing a defect in these differentiating process. The second part of our study was focused on testing a specific drug able to act on nonsense stop codon mutation, one of the most diffuse alterations in SDS patients, linked to risk of developing myelodysplastic syndrome. We successfully obtained restoration of SBDS protein in different cell lineages deriving from patients (Lymphoblastoids, MSCs, mononuclear cells from bone marrow). Protein restoration was also accompanied in some cases with an improvement of functionality. In particular, mononuclear cells from bone marrow treated with drug showed an increase in their ability to form colonies when cultured in a specific assay. This represents a powerful result, due to the potential clinical consequences related to possible therapeutic strategy. Indeed, SDS patients in future could take advantage of this drug to ameliorate their hematological defects and abolish other symptoms.

A novel mouse mutant was identified through an ENU (N-ethyl-N-nitrosourea) mutagenesis screen due to an abnormal gait. Next generation sequencing revealed the causative mutation to be in the gene Efl1 (K983R). The protein EFL1 is involved in ribosome maturation, a cellular process that is defective in diseases collectively known as ribosomopathies. More specifically, EFL1 is critical for the release of anti-association factor eIF6 from the 60S subunit, which allows subsequent joining with the 40S subunit to form a translationally active particle. Shwachman Diamond syndrome (SDS) is a ribosomopathy in which this process is known to be defective. SDS is an autosomal recessive disorder typified by bone marrow failure, pancreatic insufficiency and various anaemias. 90% of patients with SDS have missense mutations in the gene SBDS. The protein SBDS, together with EFL1, binds to the 60S subunit and causes the release of the anti-association factor eIF6. Both SBDS and EFL1 are needed for this process to occur correctly. In patients with SDS, eIF6 release is impaired due to a deficiency of functional SBDS, thus causing a ribosomal joining defect. Current research into SDS focuses on yeast models or conditional knockout/embryonic mouse models. However, this gives a limited view of the disorder as it does not reflect the multi-system nature or temporal aspects of SDS. In depth phenotypic characterisation of the Efl1-K983R mouse-line has revealed many phenotypes that reflect human SDS symptoms, such as small size, various haematological abnormalities, reduced bone mass density, deafness secondary to otitis media and behavioural deviations. At the molecular level, impaired eIF6 release has been demonstrated in mouse embryonic fibroblasts and liver. Multiple tissues from mutant mice show severe EFL-1 deficiency, suggesting that these symptoms may be reflective of the SBDS deficiency seen in SDS patients. Approximately 10% of SDS patients do not have SBDS mutations, and these patients are referred to as having 'genetically undefined' SDS. The cause of patients symptoms in these cases are unclear, and no causative gene has been found. Here we present data that suggests that Efl1 may be a candidate gene for 'genetically undefined' SDS. The data presented here also suggests that this mouse represents an opportunity to study SDS-like processes in a long lived, multi-system mammalian model, which is otherwise unavailable for Sbds mutants.

Le syndrome de Shwachman Diamond (SDS) est une ribosomopathie génétique rare entraînant une altération de la synthèse protéique associée à de nombreux symptômes, notamment une insuffisance médullaire et une neutropénie pouvant évoluer vers un syndrome de myélodysplasie ou une leucémie myéloïde aiguë. Les mutations bialléliques du gène SBDS sont responsables de plus de 90 % des cas de SDS et nous avons récemment identifié des mutations bialléliques EFL1 comme une nouvelle cause génétique de SDS. SBDS et EFL1 évincent le facteur elF6 de la sous-unité ribosomale pré60S, permettant à cette dernière d'interagir avec la sous-unité 40S pour former le ribosome mature 80S. L'acquisition naturelle d'événements génétiques somatiques au fil du temps participe au développement des maladies liées à l'âge et au développement des cancers. Cependant, dans les maladies mendéliennes, ces événements peuvent, dans de rares cas, contrer l'effet délétère de la mutation germinale et conférer un avantage sélectif aux cellules somatiquement modifiées, un phénomène appelé sauvetage génétique somatique (SGR). Nous avons récemment montré que plusieurs événements génétiques somatiques affectantl'expression ou la fonction d'elF6 sont fréquemment détectés dans les clones sanguins de patients atteints de SDS mais pas chez les individus sains, suggérant un mécanisme de SGR. Alors que la plupart de ces mutations somatiques induisent une déstabilisation de elF6 ou une haploinsuffisance d'EIF6, une mutation récurrente (N106S) n'affecte pas l'expression/stabilité d'elF6 mais réduit sa capacité à interagir avec la sous-unité 60S. Afin d'étudier plus en détail les conséquences fonctionnelles de l'haploinsuffisance de EIF6 et de la mutation N106S dans un contexte de SDS, j'ai introduit via CRISPR/Cas9 ces mutations dans des lignées fibroblastiques immortalisées de patients SDS et de contrôle. Ces modèles cellulaires originaux ont permis de déterminer l'impact de la mutation N106S sur la la localisation et la fonction d'elF6 mais aussi de préciser les effets de ces mutations sur plusieurs aspects du « fitness » cellulaire, notamment la biogenèse des ribosomes, le taux de traduction et la prolifération cellulaire. Dans l'ensemble, le développement de ce modèle a aidé à caractériser comment la mutation N106S et l'haploinsuffisance somatique de elF6 confèrent un avantage sélectif dans les cellules déficientes en SBDS ou EFL1
Shwachman Diamond syndrome (SDS) is a rare genetic ribosomopathy leading to impaired protein synthesis, which causes numerous symptoms including bone marrow failure and neutropenia that can evolve to myelodysplasia syndrome or acute myeloid leukaemia. Biallelic mutations in the SBDS gene are responsible of above 90% of the SDS cases and we recently identified biallelic EFL1 mutations as a novel cause of SDS. SBDS together with EFL1 remove the anti-association factor elF6 from the pre60S ribosomal subunit, allowing its interaction with the 40S subunit to form the mature ribosome 80S. Natural acquisition of somatic genetic events over time participâtes to age-related diseases and cancer development. However, in Mendelian diseases these events can, in rare case, counteract the deleterious effect of the germline mutation and provide a sélective advantage to the somatically modified cells, a phenomenon dubbed Somatic Genetic Rescue (SGR). We recently showed that several somatic genetic events affecting the expression or function of elF6 are frequently detected in blood clones from SDS patients but not in healthy individuals, suggesting a mechanism of SGR. While most of these somatic mutations induce elF6 destabilization or EIF6 haploinsufficiency, one récurrent mutation (N106S) did not affect the expression of elF6 but rather impact its ability to interact with the 60S subunit. In order to further investigate the functional conséquences of ElF6 haploinsufficiency and N106S mutation in a context of SDS, I introduced via CRISPR/Cas9 these mutations in immortalized fibroblastic cell line from SDS patients and control. These original cellular models hâve made it possible to détermine the impact of the N106S mutation on the localisation and function of elF6 and also to clarify the effects of these mutations on several aspects of cellular fitness, in particular ribosome biogenesis, translation rate and cell prolifération. Overall, the development of these cellular models has helped to characterise how the somatic N106S mutation and elF6 haploinsufficiency confer a sélective advantage in cells déficient in SBDS or EFL1

Research was carried out to consider the cognitive, learning and behavioural impact of Shwachman-Oiamond Syndrome (SOS) on children and adolescents. Although a physical condition, it is increasingly suspected to produce significant psychological and behavioural effects. Anecdotal evidence suggested that children with SOS had similar cognitive, behavioural and social presentations that differed from the normal population, suggesting developmental patterns that may result from SOS. Research to confirm the presence of such patterns would provide information to support the development of appropriate psychological and educational strategies for children and their families. The findings may also initiate the establishment of an indicatory tool towards a formal diagnosis. Standardised tests considering cognitive and academic ability were administered to 22 children diagnosed with SOS, aged 6 to 16. The results were compared with normative data using one-sample t-tests. Further standardised questionnaires assessed quality of life, self-concept and resiliency, and the results were compared to normative data and to a quasicontrol group diagnosed with cystic fibrosis (CF), to control for having a chronic illness. Additionally, all the children's parents completed questionnaires on their child's quality of life, behaviour and executive function, and the results from both groups were compared with each other and to normative data. The results for SOS children showed a significant difference compared to the quasi-control and normative data across all the target dimensions, apart from variables of mood and resiliency. Quality of life and self-concept scores were significantly lower in the SOS group than in the normal population or the CF group. Social skills and integration also appeared negatively affected in SOS. Thus, children with SOS appeared to follow similar cognitive and behavioural trends that differed significantly from the normal population, providing potentially recognisable patterns to aid diagnosis. The thesis also considers some limitations of the study and suggests further potential research

La sindrome Shawachman-Diamond (SDS) è una malattia multi-organo caratterizzata da disfunzioni midollari ed insufficienza pancreatica. I pazienti SDS sono inoltre soggetti a sviluppo di anomalie ematologiche gravi, quali neutropenia, SMD e/o LMA. Nella prima parte di questo lavoro ci siano focalizzati sullo studio dell’alterata capacità angiogenica in vitro delle MSCs derivate da pazienti SDS. L’angiogenesi non coinvolge solo la patogenesi dei tumori solidi, ma anche lo sviluppo delle malattie ematologiche. Le MSCs sono in grado di supportare l’angiogenesi attraverso il differenziamento cellulare, l’interazione cellula-cellula e mediante meccanismi autocrini o paracrini. Grazie a modelli in vivo ed in vitro, il nostro gruppo di ricerca ha recentemente dimostrato come le SDS-MSCs siano caratterizzate da un alterato potenziale angiogenico. Qui, abbiamo confermato l’anomala capacità angiogenica in vitro delle cellule mesenchimali SDS dopo stimolazione angiogenica. Abbiamo dimostrato come questa alterazione sia associata a cambiamenti nel pathway di segnalazione TGFβ1/VEGFA. Infatti, l’espressione di diversi fattori di crescita in grado di stimolare il rilascio endogeno di VEGFA ed in grado di essere indotti da TGFβ1 è down-regolata nelle SDS- vs HD-MSCs. Inoltre, la somministrazione esogena di TGFβ1 o VEGFA permette la reversione del fenotipo angiogenico solo nelle cellule mesenchimali derivanti dai pazienti gravemente neutropenici. In fine, abbiamo dimostrano che a seguito di stimolo angiogenico i livelli proteici di P53 sono raddoppiati nelle SDS-MSCs vs HD-MSCs, analogamente al numero di cellule in apoptosi precoce e tardiva. Complessivamente, i nostri dati indicano un forte collegamento tra TGFβ1 e VEGFA nella modulazione dell’alterata capacità in vitro delle SDS-MSCs. Inoltre, forniscono un razionale per futuri studi mirati alla comprensione della correlazione tra angiogenesi e grado di neutropenia dei pazienti. Una migliore comprensione dei meccanismi molecolari alla base della regolazione del numero e della funzionalità dei neutrofili potrebbe portare a nuove strategie terapeutiche atte alla gestione delle infezioni ricorrenti dei pazienti SDS. La seconda parte del lavoro, invece, si è focalizzata sull’analisi dei meccanismi molecolari e dei pathways di segnalazione responsabili della neutropenia e dell’evoluzione SMD o LMA dei pazienti SDS. STAT3 è un regolatore di diversi processi cellulari, quali granulogenesi dei neutrofili, leucemia e trasformazione maligna del linfoma. Inizialmente riconosciuto come un fattore di trascrizione attivato da IL6, oggi è anche considerato un substrato diretto di mTOR. Recentemente, è stato dimostrato che mTOR e STAT3 sono costitutivamente up-regolati in leucociti primari e linee cellulari linfoblastoidi derivati da pazienti SDS. In questo lavoro, dimostriamo che la via di segnalazione mTOR-STAT3 è up-regolata anche in altre tipologie cellulari appartenenti alla linea linfoide dei pazienti SDS. Inoltre, i nostri dati rivelano elevati livelli di IL6 sia in surnatanti cellulari derivanti da linfoblasti, cellule mononucleate di midollo osseo e mesenchimali, sia in campioni di plasma ottenuti da una coorte di 10 pazienti SDS. Da notare che, l’inibizione di mTOR mediata da everolimus riporta a livelli basali la fosforilazione di STAT3. In ultimo, l’inibizione di mTOR-STAT3 porta alla normalizzazione dei livelli di espressione di IL6. Complessivamente, i nostri dati rafforzano l’ipotesi che la sindrome SDS interessa sia il compartimento linfoide che mieloide e suggerisce everolimus come potenziale agente terapeutico per ridurre l’eccessiva attivazione del pathway mTOR-STAT3 [Vella A., et al. 2020]. La scoperta di nuove alterazioni nei pathway molecolari che regolano la sindrome SDS potrebbe permettere l’individuazione di target terapeutici mirati al miglioramento delle alterazioni ematologiche ed all’evoluzione leucemica di questi pazienti.
Shwachman-Diamond Syndrome (SDS, OMIM 260400) is a multi-organ disorder mainly characterized by bone marrow (BM) dysfunctions and exocrine pancreatic insufficiency. SDS patients present also severe haematologic abnormalities, with neutropenia as the most common deficiency. Of note, SDS patients have an increased risk for myelodysplastic syndrome (MDS) and malignant transformation to acute myeloid leukaemia (AML). In the first part of this work, we focused our attention on the in vitro angiogenic capability of SDS-mesenchymal stromal cells (MSCs). Angiogenesis is not only involved in the pathogenesis of solid tumours, but also in haematological malignancies. MSCs can potentiate angiogenesis via direct cell differentiation, cell-cell interaction, and autocrine or paracrine effects. Using both in vitro and in vivo models, our research group recently demonstrated that SDS-MSCs display a marked impairment in their angiogenic potential. Here, we confirm that SDS-derived cells obtained from a cohort of 10 patients show altered angiogenic properties in response to angiogenic stimuli and that the defective in vitro tube formation is associated with TGFβ1/VEGFA signalling abnormalities. Indeed, we show that the expression of several growth factors able to increase the endogenous release of VEGFA and to be induced by TGFβ1 is down-regulated in SDS- vs HD-MSCs. Moreover, by providing the exogenous administration of VEGFA or TGFβ1, we demonstrate that only SDS-MSCs from severely neutropenic patients can restore their angiogenic properties. Finally, our data also show that under angiogenic stimulation, P53 protein levels are 2-fold increase in SDS- vs HD-MSCs, as well as the number of early/late apoptotic cells. Collectively, our results suggest a strong link between TGFβ1 and VEGFA in dictating the altered in vitro angiogenic capability of SDS-MSCs. Moreover, we provide a rational to investigate whether the defective angiogenesis driven by SDS-MSCs could be related to neutropenia. The better comprehension of the molecular mechanisms regulating neutrophil number and functionality may lead to novel strategies for the management of recurrent SDS infections. The second part of our study was focused on the analysis of the molecular mechanisms and signalling pathways responsible of SDS patients neutropenia, and evolution to MDS or AML. Signal transducer and activator of transcription 3 (STAT3) is a key regulator of several cellular processes including neutrophil granulogenesis, leukaemia, and lymphoma malignant transformation. Firstly recognised as an interleukin-6 (IL6)-activated transcription factor, nowadays STAT3 is also considered a direct substrate for the mammalian target of rapamycin (mTOR). Recently, it has been demonstrated that both mTOR and STAT3 pathways are constitutively up-regulated in primary leukocytes and lymphoblastoid cell lines derived from SDS patients. Here, we show that mTOR-STAT3 signalling is markedly up-regulated in several cell subsets belonging to the lymphoid compartment of SDS patients. Furthermore, our data reveal elevated IL6 levels in cellular supernatants obtained from lymphoblasts, bone marrow mononuclear and mesenchymal stromal cells, and plasma samples obtained from a cohort of 10 patients. Of note, everolimus-mediated inhibition of mTOR signalling was associated with the basal state of phosphorylated STAT3. Finally, inhibition of mTOR-STAT3 pathway leads to normalization of IL6 expression in SDS cells. Altogether, our data strengthen the hypothesis that SDS affects both lymphoid and myeloid blood compartment and suggest everolimus as a potential therapeutic agent to reduce excessive mTOR-STAT3 activation in SDS [Vella A., et al. 2020]. The discovery of new altered molecular pathways underlying SDS pathophysiology could lead to the identification of new therapeutic targets for the correction of SDS-related haematological defects and the prevention of leukemic evolution.

Anemia occurs in 60% of patients with Shwachman Diamond Syndrome (SDS). Although bi-allelic mutations in SBDS cause SDS, it is unclear whether SBDS is critical for erythropoiesis and what the pathogenesis of anemia is in SDS. I hypothesize that SBDS protects early erythroid progenitors from p53 family member mediated apoptosis by promoting ribosome biosynthesis and translation. SBDS deficiency by vector-based shRNA led to impaired cell expansion of differentiating K562 cells due to accelerated apoptosis and reduced proliferation. Furthermore, the cells showed general reduction of 40S, 60S, 80S ribosomal subunits, loss of polysomes and impaired global translation during differentiation. An upregulation of the pro-apoptotic p53 family member, TAp73, was found in resting SBDS deficient cells; however, not in differentiating cells. These results demonstrate SBDS plays a critical role in erythroid expansion by promoting survival of early erythroid progenitors and in maintaining ribosome biogenesis during erythroid maturation independently of p53 family members.