Biology subjects

Flanagan, S. E.

Publications and source records attributed to Flanagan, S. E..

4 recordsLinked to original sources

bioRxiv2020

Male-biased islet β cell dysfunction is caused by the MODY MAFA S64F variant inducing premature aging and senescence

A heterozygous missense mutation producing a variant of the islet {beta}-cell-enriched MAFA transcription factor (Ser(S)64Phe(F) MAFA) was identified in humans who developed adult-onset, {beta}-cell dysfunction (diabetes or insulinomatosis), with men more prone to diabetes. This mutation engenders increased stability to the normally unstable MAFA protein. To obtain insight into how this variant impacts {beta} cell function, we developed a mouse model expressing S64F MafA and found sex-dependent phenotypes, with heterozygous mutant males displaying impaired glucose tolerance while females were slightly hypoglycemic with improved blood glucose clearance. Only heterozygous males showed transiently higher MafA protein levels preceding the onset of glucose intolerance and sex-dependent, differential expression of genes involved in calcium signaling, DNA damage, aging, and senescence. Functional changes in islet calcium handling and signs of islet aging and senescence processes were uniquely observed in male animals. In addition, S64F MAFA expression in human, male EndoC-{beta}H2 {beta} cells accelerated cellular senescence and increased production of senescence-associated secretory proteins compared to cells expressing wild-type MAFA. Together, these results implicate a conserved mechanism of accelerated islet aging and senescence in promoting diabetes in S64F MAFA carriers in a sex-dependent manner.

molecular biology↗

bioRxiv2019

SavvyCNV: genome-wide CNV calling from off-target reads

Identifying copy number variants (CNVS) can provide diagnoses to patients and provide important biological insights into human health and disease. Current exome and targeted sequencing approaches cannot detect clinically and biologically-relevant CNVs outside their target area. We present SavvyCNV, a tool which uses off-target read data to call CNVs genome-wide. Up to 70% of sequencing reads from exome and targeted sequencing fall outside the targeted regions - SavvyCNV exploits this free data.\n\nWe benchmarked SavvyCNV using truth sets generated from genome sequencing data and Multiplex Ligation-dependent Probe Amplification assays. SavvyCNV called CNVs with high precision and recall, outperforming five state-of-the-art CNV callers at calling CNVs genome-wide using off-target or on-target reads from targeted panel and exome sequencing. Furthermore SavvyCNV was able to call previously undetected clinically-relevant CNVs from targeted panel data highlighting the utility of this tool within the diagnostic setting. SavvyCNV is freely available.

bioinformatics↗

bioRxiv2018

Comprehensive screening shows that mutations in the known syndromic genes are rare in individuals presenting with hyperinsulinaemic hypoglycaemia

ObjectiveHyperinsulinaemic hypoglycaemia (HH) can occur in isolation or more rarely feature as part of a syndrome. Screening for mutations in the syndromic HH genes is guided by phenotype with genetic testing used to confirm the clinical diagnosis. As HH can be the presenting feature of a syndrome it is possible that mutations will be missed as these genes are not routinely screened in all newly diagnosed individuals. We investigated the frequency of pathogenic variants in syndromic genes in individuals with HH who had not been clinically diagnosed with a syndromic disorder at referral for genetic testing.\n\nDesignWe used genome sequencing data to assess the prevalence of mutations in syndromic HH genes in an international cohort of patients with HH of unknown genetic cause.\n\nMethodsWe undertook genome sequencing in 82 individuals with HH without a clinical diagnosis of a known syndrome at referral for genetic testing. Within this cohort we searched for the genetic aetiologies causing 20 different syndromes where HH had been reported as a feature.\n\nResultsWe identified a pathogenic KMT2D variant in a patient with HH diagnosed at birth, confirming a genetic diagnosis of Kabuki syndrome. Clinical data received following the identification of the mutation highlighted additional features consistent with the genetic diagnosis. Pathogenic variants were not identified in the remainder of the cohort.\n\nConclusionsPathogenic variants in the syndromic HH genes are rare but should be considered in newly diagnosed individuals as HH may be the presenting feature.

genetics↗

bioRxiv2017

Heterozygous RFX6 protein truncating variants cause Maturity-Onset Diabetes of the Young (MODY) with reduced penetrance

Finding new genetic causes of monogenic diabetes can help to understand development and function of the human pancreas. We aimed to find novel protein-truncating variants causing Maturity-Onset Diabetes of the Young (MODY), a subtype of monogenic diabetes. We used a combination of next-generation sequencing of MODY cases with unknown aetiology along with comparisons to the ExAC database to identify new MODY genes. In the discovery cohort of 36 European patients, we identified two probands with novel RFX6 heterozygous nonsense variants. RFX6 protein truncating variants were enriched in the MODY discovery cohort compared to the European control population within ExAC (odds ratio, OR=131, P=lxl0-4). We found similar results in non-Finnish European (n=348, OR=43, P=5xl0-5) and Finnish (n=80, OR=22, P=1xl0-6) replication cohorts. The overall meta-analysis OR was 34 (P=lxl0-16). RFX6 heterozygotes had reduced penetrance of diabetes compared to common HNF1A and HNF4A-MODY mutations (27%, 70% and 55% at 25 years of age, respectively). The hyperglycaemia resulted from beta-cell dysfunction and was associated with lower fasting and stimulated gastric inhibitory polypeptide (GIP) levels. Our study demonstrates that heterozygous RFX6 protein truncating variants are associated with MODY with reduced penetrance.

genetics↗