Biology subjects

Jagannathan, V.

Publications and source records attributed to Jagannathan, V..

7 recordsLinked to original sources

bioRxiv2026

Phloiokeratosis - a new ichthyosiform hyperkeratotic cornification disorder in dogs with SUV39H1 variants

The continuous renewal of healthy epidermis depends on the finely regulated proliferation of basal keratinocytes and subsequent differentiation as the newly formed cells move upwards through the different layers of the epidermis. Perturbations in keratinocyte differentiation may lead to cornification disorders. We investigated seven dogs of different breeds belonging to four independent families that showed striking multifocal tree bark-like skin lesions. Histopathologically, lesional skin was characterized by pronounced epidermal and infundibular hyperkeratosis with epidermal and sebaceous gland hyperplasia. We therefore tentatively termed the phenotype phloiokeratosis, derived from the Greek word phloios for tree bark and keratosis indicating abnormal keratinization. Whole genome sequencing of DNA from affected dogs revealed four independent variants in the SUV39H1 gene encoding the SUV39H1 histone lysine methyltransferase, an H3K9 methyltransferase, which is involved in epigenetic silencing of chromatin. Phloiokeratosis is inherited as an X-chromosomal semi-dominant trait. Four of the affected dogs in our study were heterozygous females and had lesion patterns reminiscent of Blaschko lines. In two of them, trio analyses experimentally confirmed de novo mutation events in the SUV39H1 gene. Previously, Suv39h1-/- knockout mice had been reported to have normal skin. So far, no human patients with SUV39H1 loss-of-function variants have been reported. The findings in SUV39H1 mutant dogs with phloiokeratosis for the first time link SUV39H1 deficiency to a heritable skin phenotype. Our study highlights the essential role of SUV39H1-mediated epigenetic silencing during normal keratinocyte differentiation and provides a unique model for further investigations. Author SummaryThe integrity of the skin depends on a balanced equilibrium of keratinocyte proliferation, differentiation, and sloughing of terminally differentiated cells into the environment requiring finely regulated changes in the global transcriptome of differentiating keratinocytes. We investigated seven dogs belonging to four different families with a new disorder of cornification characterized by tree bark-like outgrowths of the epidermis. Histopathological examinations confirmed that the outermost layer of the epidermis was thickened in affected dogs. The genetic analysis yielded four different SUV39H1 loss-of-function variants in the affected dogs from the four families. The SUV39H1 gene encodes an enzyme that is involved in the epigenetic silencing of chromatin. The newly characterized inherited skin disease in dogs is the first clinical phenotype that has been linked to SUV39H1 deficiency. Most likely, SUV39H1 deficiency leads to delayed epigenetic silencing and consequently delayed differentiation of keratinocytes. Dogs with this rare skin disease provide an improved understanding of the essential role of SUV39H1 in the epigenetic control of gene expression in skin.

genetics↗

bioRxiv2025

Evolutionary dynamics of a lethal recessive allele in reintroduced fragmented lynx populations

Conservation programs worldwide use reintroductions and translocations as management tools to support endangered species. Such efforts often face genetic challenges, as small populations and restricted gene flow can lead to inbreeding and loss of genetic diversity. Inbreeding depression is a well-known risk in small, isolated populations, where reduced genetic diversity can compromise fitness and threaten population persistence. While correlations between inbreeding and reduced fitness are well documented, so far, no causal variant for a fitness-relevant phenotype has been described in a wild population. Here, we combine long-term health and population data with genomic analyses to identify a recessive lethal allele responsible for extensive organ mineralization in young Eurasian lynx (Lynx lynx) from a reintroduced population in Switzerland. The causal variant is located in FGF23 and predicted to impair secretion of fibroblast growth factor 23, an important regulator of phosphate homeostasis. The deleterious allele was likely introduced from one of the lynx source populations and subsequently increased in frequency through founder effects and inbreeding. All three Swiss lynx populations show high inbreeding levels (FROH > 0.4), reflecting substantial loss of genetic diversity. Our findings uniquely demonstrate how demographic history, founder effects, genetic drift, and inbreeding interact to shape the fate of a recessive deleterious allele, highlighting the importance of multiscale monitoring in wildlife conservation.

evolutionary biology↗

bioRxiv2025

A missense variant in PAOX in American Staffordshire Terriers with juvenile-onset polyneuropathy

Hereditary polyneuropathies in dogs mirror many features of human Charcot-Marie-Tooth (CMT) disease and offer valuable spontaneous models for discovery of genes variants involved in this disorder. A juvenile-onset polyneuropathy (JOP) in American Staffordshire Terriers (ASTs) resembles CMT, with motor and sensory deficits, often accompanied by laryngeal paralysis. To identify the underlying genetic cause, we conducted a genome-wide association study (GWAS) with 24 affected and 53 control ASTs that identified a significant locus at the distal end of chromosome 28. Homozygosity mapping analysis further defined a critical interval spanning 11 protein-coding genes and whole-genome sequencing revealed a missense variant in the PAOX gene encoding polyamine oxidase (NC_049249.1:g.41474541G>A), leading to a glycine-to-arginine substitution at a highly conserved residue, XP_038435135.1:p.(Gly382Arg). Genotypes at this variant were homozygous alternate in 96% of the affected dogs (n=53) and either homozygous reference or heterozygous in 336 unaffected ASTs; the mutant allele was not detected in any of 2519 genomes of other dog breeds. In silico predictions consistently supported its pathogenicity, and structural modeling suggested altered substrate binding. Although PAOX expression was preserved, proteomic profiling in affected nerve tissue revealed reduced levels of myelin-associated proteins, as well as dysregulation of mitochondrial and proteasomal pathways. Our findings establish this PAOX missense variant as the likely cause of JOP in ASTs and highlight the breed as a valuable large-animal model for studying inherited peripheral neuropathies. These results expand the spectrum of genes implicated in polyneuropathies and provide a basis for genetic testing and informed breeding strategies in ASTs. Author summaryWe studied a hereditary peripheral nerve disorder in American Staffordshire Terriers characterized by exercise intolerance, coordination problems, general weakness and difficulty breathing due to laryngeal paralysis. These signs closely resemble a group of inherited diseases in people known as Charcot-Marie-Tooth disease. To understand the genetic basis of this condition in dogs, we analyzed the genomes of affected and healthy individuals. Our research led us to a single gene, PAOX, which carries a missense variant likely affecting the function of polyamine oxidase and ultimately disrupting how the nerve cells function and survive. Most affected dogs had two copies of the mutant allele, while it was absent or in only one copy in healthy dogs. Additional analyses suggested that the variant may interfere with the nerves ability to maintain their structure and function properly. The mutant allele does not appear to reduce the overall level of PAOX protein, but it may affect how the protein works. Our findings provide a new genetic test that can help breeders avoid producing affected puppies. They also highlight this condition in dogs as a valuable model for understanding similar diseases in humans.

genetics↗

bioRxiv2023

Single-cell profiling of bronchoalveolar cells reveals a Th17 signature in neutrophilic severe equine asthma

Severe equine asthma (SEA) shares clinical and pathological features with human neutrophilic asthma, serving as a rare natural model for this condition. To uncover the elusive immune mechanisms driving SEA, we performed single-cell mRNA sequencing (scRNA-seq) on cryopreserved bronchoalveolar cells from 11 Warmblood horses, five controls and six with SEA. We identified six major cell types, showing significant heterogeneity and novel subtypes. Notably, we observed monocyte-lymphocyte complexes and detected a robust Th17 signature in SEA, with CXCL13 upregulation in intermediate monocytes. Asthmatic horses exhibited expansion of the B cell population, Th17 polarization of the T cell populations, and dysregulation of genes associated with T cell function. Neutrophils demonstrated enhanced migratory capacity and heightened aptitude for neutrophil extracellular trap formation. These findings provide compelling evidence for a predominant Th17 immune response in neutrophilic SEA, driven by dysregulation of monocyte and T cell genes. The dysregulated genes identified through scRNA-seq have potential as biomarkers and therapeutic targets for SEA and provide insights into human neutrophilic asthma. One Sentence SummarySingle-cell mRNA sequencing identifies a predominant Th17-mediated immune response in severe equine asthma

immunology↗

bioRxiv2020

Dog color patterns explained by modular promoters of ancient canid origin

Distinctive color patterns in dogs are an integral component of canine diversity. Color pattern differences are thought to have arisen from mutation and artificial selection during and after domestication from wolves 1,2 but important gaps remain in understanding how these patterns evolved and are genetically controlled 3,4. In other mammals, variation at the ASIP gene controls both the temporal and spatial distribution of yellow and black pigments 3,5-7. Here we identify independent regulatory modules for ventral and hair cycle ASIP expression, and we characterize their action and evolutionary origin. Structural variants define multiple alleles for each regulatory module and are combined in different ways to explain five distinctive dog color patterns. Phylogenetic analysis reveals that the haplotype combination for one of these patterns is shared with arctic white wolves and that its hair cycle-specific module likely originated from an extinct canid that diverged from grey wolves more than 2 million years before present. Natural selection for a lighter coat during the Pleistocene provided the genetic framework for widespread color variation in dogs and wolves.

genetics↗

bioRxiv2019

Identification of two independent COL5A1 variants in dogs with Ehlers Danlos syndrome

BACKGROUNDThe Ehlers Danlos syndromes (EDS) are a heterogeneous group of heritable disorders affecting connective tissues. The mutations causing the various forms of EDS in humans are well characterized, but the genetic mutations causing EDS-like clinical pathology in dogs are not known, thus hampering accurate clinical diagnosis.\n\nRESULTSClinical analysis of two independent cases of skin hyperextensibility and fragility, one with pronounced joint hypermobility was suggestive of EDS. Whole genome sequencing revealed de novo mutations of COL5A1 in both cases, confirming the diagnosis of the classical form of EDS. The heterozygous COL5A1 p.Gly1013ValfsTer260 mutation characterized in case 1 introduced a premature termination codon and would be expected to result in 1(V) mRNA nonsense-mediated mRNA decay and collagen V haploinsufficiency. While mRNA was not available from this dog, biochemical analysis of the dermis suggested reduced collagen V in the dermis and ultrastructural analysis demonstrated variability in collagen fibril diameter and the presence of collagen aggregates, termed collagen cauliflowers, consistent with COL5A1 mutations underlying classical EDS. In the second case DNA sequencing demonstrated a p.Gly1571Arg missense variant in the COL5A1 gene. While samples were not available for further analysis, such a glycine substitution would be expected to destabilize the strict molecular structure of the collagen V triple helix and thus affect protein stability and/or integration of the mutant collagen into the collagen V/collagen I heterotypic dermal fibrils.\n\nCONCLUSIONSThis is the first report of genetic variants in the COL5A1 gene causing the clinical presentation of EDS in dogs. These data provide further evidence of the important role of collagen V in dermal collagen fibrillogenesis. Importantly from the clinical perspective we show the utility of DNA sequencing, combined with the established clinical criteria, in the accurate diagnosis of EDS in dogs.

genetics↗

bioRxiv2017

Development of a high-density, 2M SNP genotyping array and 670k SNP imputation array for the domestic horse

BackgroundTo date, genome-scale analyses in the domestic horse have been limited by suboptimal single nucleotide polymorphism (SNP) density and uneven genomic coverage of the current SNP genotyping arrays. The recent availability of whole genome sequences has created the opportunity to develop a next generation, high-density equine SNP array.\n\nResultsUsing whole genome sequence from 153 individuals representing 24 distinct breeds collated by the equine genomics community, we cataloged over 23 million de novo discovered genetic variants. Leveraging genotype data from individuals with both whole genome sequence, and genotypes from lower-density, legacy SNP arrays, a subset of [~]5 million high-quality, high-density array candidate SNPs were selected based on breed representation and uniform spacing across the genome. Considering probe design recommendations from a commercial vendor (Affymetrix, now Thermo Fisher Scientific) a set of [~]2 million SNPs were selected for a next-generation high-density SNP chip (MNEc2M). Genotype data were generated using the MNEc2M array from a cohort of 332 horses from 20 breeds and a lower-density array, consisting of [~]670 thousand SNPs (MNEc670k), was designed for genotype imputation.\n\nConclusionsHere, we document the steps taken to design both the MNEc2M and MNEc670k arrays, report genomic and technical properties of these genotyping platforms, and demonstrate the imputation capabilities of these tools for the domestic horse.

genomics↗