Project description:Ion Torrent S5 was used to identify the cause of white patterning in a Standardbred horse with no known white patterning alleles. These data and sanger sequencing identified NC_009146.3:g.79545248T>A as a de novo variant causal to white spotting in a Standardbred horse.
2022-05-12 | PRJEB52700 | EVA
Project description:Novel KIT variants underlying dominant white in the Australian horse population
Project description: ABSTRACT POLR2A encodes RPB1, the largest subunit of the RNA polymerase II (pol II) complex, which is responsible for transcription of all ~21,000 protein-encoding genes. Here we describe the first fifteen patients harboring de novo heterozygous variants in POLR2A. The majority presents with profound infantile onset hypotonia and developmental delay. Missense variants that were expected to exert only mild structural effects, lead to malfunctioning RPB1, thereby inducing a dominant negative effect on pol II function. Intriguingly, these patients presented with a severe clinical phenotype. Conversely, variants expected to result in loss-of-function, leading to reduced availability of RPB1 were better tolerated: these patients exhibited the mildest phenotypes.
Project description:We previously described the KINSSHIP syndrome, an autosomal dominant disorder associated with de novo variants in the AFF3 degron , a sequence involved in its binding to ubiquitin ligase. Mouse knock-ins and overexpression in zebrafish provided evidence for a dominant-negative (DN) mode-of-action, wherein an increased level of AFF3 resulted in pathological effects. In line with this hypothesis, we describe an individual presenting a KINSSHIP-like phenotype carrying a partial duplication of AFF3. Further screening of intellectual disability cohorts revealed nine individuals with heterozygous and three with homozygous loss-of-function (LoF) variants, as well as two probands with compound LoF/missense and six with biallelic missense mutations in AFF3, who displayed a milder syndrome. Matching zebrafish knockdowns exhibit neurological defects that could be rescued by expressing human AFF3 mRNA confirming their association with the ablation of aff3. Conversely, the missense isoforms did not complement demonstrating the deleteriousness of the variants identified in affected individuals. To assess the different effect of these variants, we profiled the transcriptome of fibroblasts of affected individuals and isogenic cells harboring DN/DN, LoF/+, LoF/LoF or DN/LoF AFF3 genotypes. While the same pathways are affected, only one-third of the differentially expressed genes are common to both homozygote datasets, indicating that AFF3 LoF and DN mutations largely modulate transcriptomes differently. In particular, the apical junction and DNA repair pathways displayed opposite modulation. Our results and the high pleiotropy shown by this locus in GWASes suggest that even slight changes in the AFF3 function might be deleterious.
Project description:We previously described the KINSSHIP syndrome, an autosomal dominant disorder associated with de novo variants in the AFF3 degron , a sequence involved in its binding to ubiquitin ligase. Mouse knock-ins and overexpression in zebrafish provided evidence for a dominant-negative (DN) mode-of-action, wherein an increased level of AFF3 resulted in pathological effects. In line with this hypothesis, we describe an individual presenting a KINSSHIP-like phenotype carrying a partial duplication of AFF3. Further screening of intellectual disability cohorts revealed nine individuals with heterozygous and three with homozygous loss-of-function (LoF) variants, as well as two probands with compound LoF/missense and six with biallelic missense mutations in AFF3, who displayed a milder syndrome. Matching zebrafish knockdowns exhibit neurological defects that could be rescued by expressing human AFF3 mRNA confirming their association with the ablation of aff3. Conversely, the missense isoforms did not complement demonstrating the deleteriousness of the variants identified in affected individuals. To assess the different effect of these variants, we profiled the transcriptome of fibroblasts of affected individuals and isogenic cells harboring DN/DN, LoF/+, LoF/LoF or DN/LoF AFF3 genotypes. While the same pathways are affected, only one-third of the differentially expressed genes are common to both homozygote datasets, indicating that AFF3 LoF and DN mutations largely modulate transcriptomes differently. In particular, the apical junction and DNA repair pathways displayed opposite modulation. Our results and the high pleiotropy shown by this locus in GWASes suggest that even slight changes in the AFF3 function might be deleterious.
Project description:SF3B1 is an essential and ubiquitous splicing factor that plays a pivotal role in the early steps of pre-mRNA splicing. Recurrent somatic missense mutations in SF3B1 are frequent in cancers, but no constitutional variant has been reported so far. We describe here a cohort of 26 individuals with neurodevelopmental disorders, harbouring SF3B1 constitutional heterozygous variants that appeared mostly de novo. Patients present with a global developmental delay, associated with variable neurological and facial dysmorphic traits. A dichotomy may emerge between patients harbouring predicted loss of function (n=9) and missense variants (n=17), the latter being associated with a more severe and syndromic phenotype, including heart and gastrointestinal anomalies. We focused on de novo SF3B1 missense variants, which were largely distinct from those reported in cancer. Functional complementation assays show that de novo SF3B1 missense variants did not cause a loss of function of the protein. Targeted and genome-wide analysis of RNA splicing reveal that they affect canonical and alternative splicing more moderately than somatic variants, and subtly modify the splicing of many transcripts, some of which are involved in neurodevelopmental disorders. SF3B1 joins the short list of U2 snRNP components involved in both cancer and neurodevelopmental disorders.