Biomedical subjects

Katrina M Bell

Publications and source records attributed to Katrina M Bell.

4 recordsLinked to original sources

PubMed2026

Molecular analysis of individuals with suspected 46,XY differences of sex development in a homogenous and understudied population.

Differences of sex development (DSD) are a group of rare congenital conditions defined by atypical chromosomal, gonadal, and/or hormonal sex. Despite advances in massively parallel sequencing (MPS), more than half of DSD cases have an unknown genetic aetiology. We recruited and analysed 21 individuals with 46,XY DSD from the Greater Middle East population using chromosomal microarray and whole exome sequencing. Participants had DSD ranging from micropenis to anorchia (absence of testes) with extra-genital features reported in four individuals (19%). Using a combination of microarray and WES, a genetic diagnosis (variants curated as likely pathogenic or pathogenic) was identified in 12/21 (57%) individuals. Microarray analysis showed two DSD participants with extra genital features had chromosomal abnormalities (48,XXXY and mosaic Y chromosomal rearrangement). Microarray also indicated a high degree of consanguinity, with extensive long contiguous stretches of homozygosity (LCSH) (>3% of the genome) in 6/21 (28.6%) individuals, all of whom received a genetic diagnosis. WES analysis revealed variants in the NR5A1 (three individuals), SRD5A2 (three individuals), TALDO1 (one individual) and AR (two individuals) genes. This includes the novel frameshift variant, c.1309del (p.Leu437Cysfs*59), in NR5A1. This study contributes to the characterisation of clinical features and molecular findings in individuals with DSD in this understudied and homogenous population and highlights the challenges with DSD diagnosis in the region. The genetic diagnoses identified may contribute to improved patient care and management.

Humans↗

PubMed2026

Elucidating the Role of SET as a Key Contributor to Neurodevelopmental Disability Within the 9q34.11 Deletion Syndrome Interval.

The 9q34.11 chromosomal region contains multiple neurodevelopmental genes involved in synaptic transmission, axonal structure and neuronal maturation. Pathogenic microdeletions, duplications and single nucleotide variants in numerous genes were previously linked with neurodevelopmental disorders (NDDs). Amongst them, SET has recently been implicated in a rare NDD with speech delay and facial dysmorphism. This study reports a female with a heterozygous de novo deletion impacting SET but not other NDD-associated genes at 9q34.11. The proband was initially diagnosed with atypical Rett syndrome with overlapping clinical features of SET haploinsufficiency. The deletion was confirmed using microarray and long-read sequencing. Subsequent quantitative proteomic evaluation identified a significant decrease of SET protein in patient-derived fibroblasts compared to control lines. This study provides insights into the proband's clinical course over their 28 year diagnostic odyssey, and emphasises the benefits of early speech therapy interventions. The proband had no functional speech, but regained the capacity to meaningfully communicate and articulate a limited vocabulary in adulthood, concordant with other reported non-paediatric cases of SET-NDD. This study expands current knowledge on the genotypic and phenotypic spectra of SET-NDD, and pinpoints a smaller 9q34.11 critical region excluding upstream NDD-associated genes, STXBP1 and SPTAN1, implicating SET as a significant NDD-associated gene.

Humans↗

PubMed2026

Structural variant discovery and diagnostic impact in rare diseases from short-read and long-read sequencing.

Rare diseases collectively affect 1 in 10 individuals, yet current genetic testing fails to identify a causal variant for most cases. At present, cytogenetic methods and/or sequencing approaches such as exome (ES) or short-read genome sequencing (srGS) represent the state-of-the-art for comprehensive clinical discovery of sequence and structural variants (SVs), including copy number variants, balanced SVs, complex SVs, and tandem repeats (TRs). Recently, long-read genome sequencing (lrGS), coupled with multiomics data, has presented great promise to resolve variation in genomic regions recalcitrant to characterization by srGS such as highly repetitive simple repeat sequences and segmental duplications. However, there are few guidelines to enable clinical interpretation of genetic variation in these highly repetitive genomic regions, and the enthusiasm of the field in adopting lrGS has made it difficult to assess the true added diagnostic yield of this technology due to widely variable and inconsistently applied analytic pipelines and variable degrees of pre-screening by ES or srGS. Here, we investigated the contribution of SVs to rare diseases using srGS as a front-line strategy when paired with highly sensitive SV discovery and evaluate the added diagnostic yield of incorporating lrGS for a subset of cases. Our srGS analysis encompassed 1,462 families (3,450 individuals) recruited through the Broad Institute Center for Mendelian Genetics and the Genomics Research to Elucidate the Genetics of Rare Diseases (GREGoR) programs. Diagnostic SVs were identified in 5.4% of cases (79/1,462), of which 80% were uniquely detectable by srGS compared to standard cytogenetic techniques. For 96 families (including 10 families with a heterozygous variant observed in a known recessive gene of clinical relevance), we performed lrGS with methylation profiling, as well as long-read transcriptomic analyses in a subset of 20 trios. Analyses with lrGS yielded over 25,000 SVs per genome, 63% of which were not captured by srGS, along with an additional ~200 rare SNV/indels per genome not previously captured and 12 differentially methylated regions per genome. Among these, we identified only one diagnostic variant not interpreted by srGS, an apparently mosaic de novo SNV in CASK that was absent in the srGS callset due to allelic imbalance. No new diagnoses were supported by long-read transcriptomics or episignatures. In this well characterized rare disease cohort, the added diagnostic yield was thus 1.04% (1/96 families). Following a systematic literature review of prior lrGS studies, we find that most reported diagnoses were detectable by srGS and that our added diagnostic yield is consistent with those prior studies. These studies emphasize the significant impact of comprehensive SV discovery in rare disease cases and further demonstrate the power for increased discovery of novel genomic variation and episignatures from lrGS. Nonetheless, they also serve to temper expectations of dramatic diagnostic advances in rare disease patients until there is more extensive annotation of the functional and clinical impact of all coding and noncoding variation uniquely accessible to lrGS with extensive reference databases spanning highly repetitive genomic sequencing that could be enabled by this transformative technology.

Journal Article↗

PubMed2026

Unraveling a Diagnostic Enigma: A TECPR2 Case Solved Through Multi-Omic Genomics.

TECPR2 is a key regulator of autophagy, encoded by the TECPR2 gene. Pathogenic variants in this gene have been linked to a rare hereditary sensory and autonomic neuropathy with intellectual disability (HSAN9). We report a teenage female with a syndromic intellectual disability disorder associated with neuromuscular abnormalities. Multi-omics analysis including genomics, transcriptomics, and proteomics, together with muscle biopsy from the affected individual, were used in this clinical case. Through trio exome sequencing we identified two heterozygous variants in the TECPR2 gene, NM_014844.4: c.480G>A; p.(Gln160=) and c.2846C>A; p.(Ala949Glu). Both were classified as variants of uncertain significance due to the lack of supporting evidence for pathogenicity. Subsequent long-read sequencing phased the variants and confirmed they were in trans. Additional functional studies using RNAseq and proteomics analyses verified the pathogenicity of the variants. This case study demonstrated the value of a multi-omics assisted analysis, which complemented the traditional phenotype-first approach in reaching a definitive clinical diagnosis.

Humans↗