Newburger, P. E. | Search bioRxiv

bioRxiv2026

Cytopenias and Functional Defects in a Novel Murine Model of VPS45 Severe Congenital Neutropenia

Mutations in the VPS45 gene are associated with a rare form of severe congenital neutropenia (SCN5), a life-threatening inherited error of immunity. We developed and characterized a novel mouse model of SCN5 by CRISPR/Cas9-mediated knock-in of pathogenic VPS45 E238K and T224N mutations. Both Vps45 mutations led to decreased protein expression in bone marrow cells. In vivo phenotyping demonstrated a non-Mendelian genetic distribution with reduced numbers of knock-in homozygotes Vps45E238K. Vps45E238K knock-in homozygous mice showed reduced body weight, reduced body condition with age, and increased mortality. As in human SCN5, Vps45E238K knock-in homozygotes demonstrated neutropenia and lymphopenia. Functionally, Vps45E238K knock-in homozygote neutrophils exhibited increased lipopolysaccharide-induced apoptosis and decreased peroxide production, phagocytic capacity and in vivo cell migration, phenocopying the functional defects reported in patients. Vps45T224N knock-in homozygous mice showed a milder phenotype or no abnormalities. In conclusion, this mouse model phenocopies, in part, human SCN5. It provides a novel platform for future studies of the pathophysiology of defects in neutrophil number and function in human SCN5, potential therapies for the disease, and the biochemistry and cell biology of VPS45. Summary statementWe report a mouse model of severe congenital neutropenia due to VPS45 missense mutations. It represents the first animal model of human neutropenia due to a defect in intracellular trafficking.

immunology↗

bioRxiv2018

The Genetic Landscape of Diamond-Blackfan Anemia

Diamond-Blackfan anemia (DBA) is a rare bone marrow failure disorder that affects 1 in 100,000 to 200,000 live births and has been associated with mutations in components of the ribosome. In order to characterize the genetic landscape of this genetically heterogeneous disorder, we recruited a cohort of 472 individuals with a clinical diagnosis of DBA and performed whole exome sequencing (WES). Overall, we identified rare and predicted damaging mutations in likely causal genes for 78% of individuals. The majority of mutations were singletons, absent from population databases, predicted to cause loss of function, and in one of 19 previously reported genes encoding for a diverse set of ribosomal proteins (RPs). Using WES exon coverage estimates, we were able to identify and validate 31 deletions in DBA associated genes. We also observed an enrichment for extended splice site mutations and validated the diverse effects of these mutations using RNA sequencing in patientderived cell lines. Leveraging the size of our cohort, we observed several robust genotype-phenotype associations with congenital abnormalities and treatment outcomes. In addition to comprehensively identifying mutations in known genes, we further identified rare mutations in 7 previously unreported RP genes that may cause DBA. We also identified several distinct disorders that appear to phenocopy DBA, including 9 individuals with biallelic CECR1 mutations that result in deficiency of ADA2. However, no new genes were identified at exome-wide significance, suggesting that there are no unidentified genes containing mutations readily identified by WES that explain > 5% of DBA cases. Overall, this comprehensive report should not only inform clinical practice for DBA patients, but also the design and analysis of future rare variant studies for heterogeneous Mendelian disorders.

genetics↗