Biology subjects

Sethna, S.

Publications and source records attributed to Sethna, S..

3 recordsLinked to original sources

bioRxiv2023

Gene Therapy Mediated Partial Reprogramming Extends Lifespan and Reverses Age-Related Changes in Aged Mice

Aging is a complex process best characterized as the chronic dysregulation of cellular processes leading to deteriorated tissue and organ function. While aging cannot currently be prevented, its impact on lifespan and healthspan in the elderly can potentially be minimized by interventions that aim to return these cellular processes to optimal function. Recent studies have demonstrated that partial reprogramming using the Yamanaka factors (or a subset; OCT4, SOX2, and KLF4; OSK) can reverse age-related changes in vitro and in vivo. However, it is still unknown whether the Yamanaka factors (or a subset) are capable of extending the lifespan of aged wild type mice. Here, we show that systemically delivered AAVs, encoding an inducible OSK system, in 124-week-old mice extends the median remaining lifespan by 109% over wild-type controls and enhances several health parameters. Importantly, we observed a significant improvement in frailty scores indicating that we were able to improve the healthspan along with increasing the lifespan. Furthermore, in human keratinocytes expressing exogenous OSK, we observed significant epigenetic markers of age-reversal, suggesting a potential reregulation of genetic networks to a younger, potentially healthier state. Together, these results may have important implications for the development of partial reprogramming interventions to reverse age-associated diseases in the elderly.

bioengineering↗

bioRxiv2021

Potential therapy for progressive vision loss due to PCDH15-associated Usher syndrome developed in an orthologous Usher mouse

Usher syndrome type I (USH1) is characterized by congenital deafness, vestibular areflexia, and progressive retinal degeneration with age. The protein-truncating p.Arg245* founder variant of PCDH15 has an ~2% carrier frequency among Ashkenazi Jews, accounting for nearly 60% of their USH1 cases. Here, longitudinal ocular phenotyping in thirteen USH1F individuals harboring the p.Arg245* variant revealed progressive retinal degeneration, leading to severe loss of vision with macular atrophy by the sixth decade. Half of the affected individuals met either the visual acuity or visual field loss definition for legal blindness by the middle of their fifth decade of life. Mice homozygous for p.Arg250* (Pcdh15R250X; equivalent to human p.Arg245*) also have early visual deficits evaluated using electroretinography. Light-dependent translocation of phototransduction cascade proteins, arrestin and transducin, was found to be impaired in Pcdh15R250X mice. Retinal pigment epithelium-(RPE) specific visual retinoid cycle proteins, RPE65 which converts all-trans retinoids to 11-cis retinoids and CRALBP that transports retinoids, and key retinoid levels were also reduced in Pcdh15R250X mice, suggesting a dual role for protocadherin-15 in photoreceptors and RPE. Administration of exogenous 9-cis retinal, an analog of the naturally occurring 11-cis retinal, improved ERG amplitudes in these mutant mice, suggesting a basis for a clinical trial of exogenous FDA approved retinoids to preserve vision in USH1F patients. SummaryIn a preclinical setting studying exogenous retinoids using a novel Usher syndrome mouse model, we describe a potential therapy to treat PCDH15-mediated visual dysfunction.

neuroscience↗

bioRxiv2018

Genomic knockout of alms1 in zebrafish recapitulates Alstrom syndrome and provides insight into metabolic phenotypes

SCIENTIFIC ABSTRACTAlstrom syndrome is an autosomal recessive obesity ciliopathy caused by loss-of-function mutations in the ALMS1 gene. In addition to multi-organ dysfunction, such as cardiomyopathy, retinal degeneration, and renal dysfunction, the disorder is characterized by high rates of obesity, insulin resistance and early onset type 2 diabetes mellitus (T2DM). To investigate mechanisms linking disease phenotypes we generated a loss-of-function deletion of alms1 in the zebrafish using CRISPR/Cas9. We demonstrate conserved phenotypic effects including cardiac defects, retinal degeneration, and metabolic deficits that included propensity for obesity and fatty livers in addition to hyperinsulinemia and glucose response defects. Gene expression changes in {beta}-cells isolated from alms1-/- mutants revealed changes consistent with insulin hyper-secretion and glucose sensing failure, which were also identified in cultured murine {beta}-cells lacking Alms1. These data present a zebrafish model to assess etiology and new secretory pathway defects underlying Alstrom syndrome-associated metabolic phenotypes. Given the hyperinsulinemia and reduced glucose sensitivity in these animals we also propose the alms1 loss-of-function mutant as a monogenic model for studying T2DM phenotypes.\n\nAUTHOR SUMMARYThese data comprise a thorough characterization of a zebrafish model of Alstrom syndrome, a human obesity syndrome caused by loss-of-function deletions in a single gene, ALMS1. The high rates of obesity and insulin resistance found in these patients suggest this disorder as a single-gene model for Type 2 Diabetes Mellitus (T2DM), a disorder caused by a variety of environmental and genetic factors in the general population. We identify a propensity for obesity, excess lipid storage, loss of {beta}-cells in islets, and hyperinsulinemia in larval and adult stages of zebrafish alms1 mutants. We isolated {beta}-cells from the alms1 mutants and compared the gene expression profiles from RNASeq datasets to identify molecular pathways that may contribute to the loss of {beta}-cells and hyperinsulinemia. The increase in genes implicated in generalized pancreatic secretion, insulin secretion, and glucose transport suggest potential {beta}-cell exhaustion as a source of {beta}-cell loss and excess larval insulin. We propose this mutant as a new genetic tool for understanding the metabolic failures found in Type 2 Diabetes Mellitus.

genetics↗