Genetic and genomic analyses of neurological diseases in dogs as a model of rare human diseases

L’identification des mutations génétiques impliquées dans les maladies rares est un prérequis pour mieux les comprendre, les traiter et accompagner les patients. Pour se faire, des modèles animaux présentant des maladies spontanées homologues aux maladies humaines sont très prometteurs. Le chien développe spontanément des maladies génétiques, rares chez l’Homme, mais fréquentes dans certaines races de chiens, ce qui simplifie les analyses génétiques. Ma thèse a porté sur deux maladies neurologiques : l’épilepsie et la neuropathie. Pour l’épilepsie, l’objectif était d’identifier des variants génétiques à partir de données de génotypage et de séquençage de génomes complets de deux races canines prédisposées. Un locus lié à la maladie a été identifié dans une race et des variants ponctuels et structuraux candidats ont été identifiés dans les deux races et sont en cours de validation par séquençage ciblé. Pour la neuropathie, l’équipe avait identifié une mutation en amont du gène GDNF, responsable d’une neuropathie sensitive chez des chiens de chasse. J’ai participé à la validation fonctionnelle de cette mutation. De plus, GDNF étant un excellent gène candidat pour les neuropathies humaines, j’ai séquencé ce gène chez 111 patients et extrait les variants de GDNF d’une base de données d’exomes et de génomes de plus de 600 patients. J’ai ainsi identifié 21 variants rares ou inconnus et les ai priorisé selon leurs impacts prédits in silico. Ces deux projets, alliant analyses génétiques, génomiques et fonctionnelles, chez l’homme et le chien, montrent le potentiel du chien pour l’identification de gènes candidats dans des maladies rares et/ou complexes chez l’Homme.The identification of genetic mutations involved in rare diseases is a prerequisite for a better understanding, therapies and care to patients. To this aim, animal models declaring spontaneous diseases, homologous to human diseases are very promising. Dogs spontaneously develop genetic diseases, rare in humans, but frequent in some dog breeds, which simplifies the genetic analyzes. My thesis focused on two neurological diseases: epilepsy and neuropathy. For epilepsy, the goal was to identify genetic variants from genotyping data and sequencing of whole genome of dogs from two predisposed breeds. A disease-related locus has been identified in one breed and candidate point mutations and structural variants were identified in the two breeds and are being validated by targeted sequencing. For neuropathy, the team previously identified a mutation upstream of the GDNF gene, responsible for sensory neuropathy in hunting dogs. I participated to the functional validation of this mutation. In addition, GDNF being an excellent candidate gene for human neuropathies, I sequenced this gene in 111 patients and extracted GDNF variants from a database of exomes and genomes from more than 600 patients. I identified 21 rare or unknown variants and prioritized them according to their in silico predicted impacts. These two projects, combining genetics, genomics and functional analyses, in humans and dogs, show the dog's potential for identifying candidate genes in rare and / or complex diseases in humans

A Point Mutation in a lincRNA Upstream of GDNF Is Associated to a Canine Insensitivity to Pain: A Spontaneous Model for Human Sensory Neuropathies

Human Hereditary Sensory Autonomic Neuropathies (HSANs) are characterized by insensitivity to pain, sometimes combined with self-mutilation. Strikingly, several sporting dog breeds are particularly affected by such neuropathies. Clinical signs appear in young puppies and consist of acral analgesia, with or without sudden intense licking, biting and severe self-mutilation of the feet, whereas proprioception, motor abilities and spinal reflexes remain intact. Through a Genome Wide Association Study (GWAS) with 24 affected and 30 unaffected sporting dogs using the Canine HD 170K SNP array (Illumina), we identified a 1.8 Mb homozygous locus on canine chromosome 4 (adj. p-val = 2.5x10-6). Targeted high-throughput sequencing of this locus in 4 affected and 4 unaffected dogs identified 478 variants. Only one variant perfectly segregated with the expected recessive inheritance in 300 sporting dogs of known clinical status, while it was never present in 900 unaffected dogs from 130 other breeds. This variant, located 90 kb upstream of the GDNF gene, a highly relevant neurotrophic factor candidate gene, lies in a long intergenic non-coding RNAs (lincRNA), GDNF-AS. Using human comparative genomic analysis, we observed that the canine variant maps onto an enhancer element. Quantitative RT-PCR of dorsal root ganglia RNAs of affected dogs showed a significant decrease of both GDNF mRNA and GDNF-AS expression levels (respectively 60% and 80%), as compared to unaffected dogs. We thus performed gel shift assays (EMSA) that reveal that the canine variant significantly alters the binding of regulatory elements. Altogether, these results allowed the identification in dogs of GDNF as a relevant candidate for human HSAN and insensitivity to pain, but also shed light on the regulation of GDNF transcription. Finally, such results allow proposing these sporting dog breeds as natural models for clinical trials with a double benefit for human and veterinary medicine.This study was supported by the CNRS (Centre National de la Recherche Scientifique), the Brittany Region (France) (PhD funding for JP), the European Commission (FP7-LUPA, GA-201370), the Rosembloom Family and the Companion animal health fund from the Faculté de Médecine Vétérinaire, Université de Montréal, and the CRB-Anim infrastructure, ANR-11-INBS-0003, funded by the French National Research Agency in the frame of the ‘Investing for the Future’ program.The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

JASPAR 2020: update of the open-access database of transcription factor binding profiles

JASPAR (http://jaspar.genereg.net) is an open-access database of curated, non-redundant transcription factor (TF)-binding profiles stored as position frequency matrices (PFMs) for TFs across multiple species in six taxonomic groups. In this 8th release of JASPAR, the CORE collection has been expanded with 245 new PFMs (169 for vertebrates, 42 for plants, 17 for nematodes, 10 for insects, and 7 for fungi), and 156 PFMs were updated (125 for vertebrates, 28 for plants and 3 for insects). These new profiles represent an 18% expansion compared to the previous release. JASPAR 2020 comes with a novel collection of unvalidated TF-binding profiles for which our curators did not find orthogonal supporting evidence in the literature. This collection has a dedicated web form to engage the community in the curation of unvalidated TF-binding profiles. Moreover, we created a Q&A forum to ease the communication between the user community and JASPAR curators. Finally, we updated the genomic tracks, inference tool, and TF-binding profile similarity clusters. All the data is available through the JASPAR website, its associated RESTful API, and through the JASPAR2020 R/Bioconductor package

A Point Mutation in a lincRNA Upstream of GDNF Is Associated to a Canine Insensitivity to Pain: A Spontaneous Model for Human Sensory Neuropathies

Human Hereditary Sensory Autonomic Neuropathies (HSANs) are characterized by insensitivity to pain, sometimes combined with self-mutilation. Strikingly, several sporting dog breeds are particularly affected by such neuropathies. Clinical signs appear in young puppies and consist of acral analgesia, with or without sudden intense licking, biting and severe self-mutilation of the feet, whereas proprioception, motor abilities and spinal reflexes remain intact. Through a Genome Wide Association Study (GWAS) with 24 affected and 30 unaffected sporting dogs using the Canine HD 170K SNP array (Illumina), we identified a 1.8 Mb homozygous locus on canine chromosome 4 (adj. p-val = 2.5x10-6). Targeted high-throughput sequencing of this locus in 4 affected and 4 unaffected dogs identified 478 variants. Only one variant perfectly segregated with the expected recessive inheritance in 300 sporting dogs of known clinical status, while it was never present in 900 unaffected dogs from 130 other breeds. This variant, located 90 kb upstream of the GDNF gene, a highly relevant neurotrophic factor candidate gene, lies in a long intergenic non-coding RNAs (lincRNA), GDNF-AS. Using human comparative genomic analysis, we observed that the canine variant maps onto an enhancer element. Quantitative RT-PCR of dorsal root ganglia RNAs of affected dogs showed a significant decrease of both GDNF mRNA and GDNF-AS expression levels (respectively 60% and 80%), as compared to unaffected dogs. We thus performed gel shift assays (EMSA) that reveal that the canine variant significantly alters the binding of regulatory elements. Altogether, these results allowed the identification in dogs of GDNF as a relevant candidate for human HSAN and insensitivity to pain, but also shed light on the regulation of GDNF transcription. Finally, such results allow proposing these sporting dog breeds as natural models for clinical trials with a double benefit for human and veterinary medicine.This study was supported by the CNRS (Centre National de la Recherche Scientifique), the Brittany Region (France) (PhD funding for JP), the European Commission (FP7-LUPA, GA-201370), the Rosembloom Family and the Companion animal health fund from the Faculté de Médecine Vétérinaire, Université de Montréal, and the CRB-Anim infrastructure, ANR-11-INBS-0003, funded by the French National Research Agency in the frame of the ‘Investing for the Future’ program.The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

The AMS variant affect binding of nuclear complex.

<p>EMSAs were performed with wild type (WT) or mutated (Mut) duplex and nuclear extract (NE). (A) Detection of a mobility shift after incubation of 40 fmoles of radiolabelled WT-duplex (lane 1 to 4) or Mut-duplex (lane 5 to 8) with increasing amounts (0,3–0,6–1,2–2,4 μl) of HeLa NE. (B) 40 fmoles of radiolabelled WT-duplex were incubated without (lane 9 and 13) or with 1μl of HeLa NE (lane 10 to 12) or 5 μl of SY5Y (lane 14 to 16) NE and in the presence of 2 pmol of competitor WT-duplex (lane 11 and 15) or Mut-duplex (lane 12 and 16). Black bar: specific complex associated with the radioactive duplex, asterisk: non specific complex.</p

Summary of the SNPs found in the targeted sequencing.

<p>Only variants that are homozygous for a rare allele in all affected dogs and not homozygous in controls were considered to perfectly segregate. Nb SNPs: Number of SNPs; Hom: Nb Homozygous variants; HTZ: Nb Heterozygous variants.</p

Best-SNPs obtained by GWAS using 21 affected <i>vs</i> 28 unaffected French spaniels.

<p>Best-SNPs obtained by GWAS using 21 affected <i>vs</i> 28 unaffected French spaniels.</p

Summary of the variants obtained in the targeted sequencing before and after filtering.

<p>Summary of the variants obtained in the targeted sequencing before and after filtering.</p

Association study for the acral mutilation syndrome in sporting dogs.

<p>(A) Clinical phenotype in the French spaniel breed (left picture). Dogs present insensitivity to pain in feet and can sometimes show severe self-mutilations with the absence of a toe. (B) Manhattan plot of -log10 transformed p-values by canine chromosome highlighting a strong signal on chromosome 4 (Wald test; p ≤ 10⁻¹⁶). C) Manhattan plot of -log10 empirical p-values (EMP) obtained by permutations test confirming the signal on chromosome 4 (Permutation = 100,000).</p

qRT-PCR results in Dorsal Root Ganglia using the ΔΔCt methodology (cases in grey, controls in white).

<p>Measures obtained from two DRG by individual were pooled, and we also pooled affected dogs and controls. We used <i>PPIB</i> (<i>Peptidylprolyl Isomerase B</i>) as control and all genes of the locus (<i>GDNF-AS</i>, <i>GDNF</i>, <i>WDR70</i>, <i>NUP155</i>, <i>SLC1A3</i>) were tested 3 times with 3 replicates for each (t-test: p-value *<0.0001).</p