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

Jocelyn Plassais,Maud Bizot,Solenne Correard,Pascale Quignon,Carme Arnan,Nadine Botherel,Manon Paradis,Thomas Derrien,Gilles Salbert,Alix Pommier,Philippe Pilorge,Christophe Hitte,Rory Johnson,Catherine André,Agnès Méreau,David W Silversides ,Benoît Hédan ,Laëtitia Lagoutte ,Marie‐Christine Cadiergues ,É Guaguère ,Mark E Samuels

doi:10.1371/journal.pgen.1006482

Abstract

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.

Highlights

Inherited peripheral neuropathies are neurodegenerative diseases of the peripheral nervous system (PNS), including the Charcot-Marie-Tooth diseases (CMT) and Hereditary Sensory and Autonomic Neuropathies (HSANs) [1]
We present a canine neuropathy characterized by insensitivity to pain in the feet, sometimes combined with self-mutilation described in four sporting breeds
This particular phenotype has the clinical hallmarks of human Hereditary Sensory Autonomic Neuropathies (HSAN)

Summary

Introduction

Inherited peripheral neuropathies are neurodegenerative diseases of the peripheral nervous system (PNS), including the Charcot-Marie-Tooth diseases (CMT) and Hereditary Sensory and Autonomic Neuropathies (HSANs) [1]. They are categorized based on the degree of involvement of motor, sensory and/or autonomic nerve fibers. The main symptoms correspond to a progressive degeneration of sensory and autonomic neurons causing insensitivity to pain and temperature in feet and hands, leading to ulcerative mutilations [3,4,5] These lesions could result in severe tissue infections and/or osteomyelitis and may lead to amputation of the affected limbs. 12 genes have been associated with HSANs until now, they only explain one third of the patients affected with HSANs, highlighting the fact that the genetic causes of HSANs remain only partially understood in humans [2] and that natural models of these diseases are needed

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Discussion

Conclusion