New Forest Pony (Horse) — Myotonia (hereditary; OMIA-verified breed predisposition)

Source: first-hand OMIA (University of Sydney) breed-specific hereditary-disorder record, saved verbatim to source_file; every claim below is a C1 byte-substring of it.

Claims

Breed: New Forest Pony (Horse)
Disorder:
Mode of inheritance: Autosomal recessive
Summary: As summarised by Valberg (2014), Myotonic muscle disorders share the feature of delayed relaxation of muscle after mechanical stimulation or voluntary contraction due to abnormal muscle membrane conduction. Horses have three known forms of myotonia: myotonia congenita, myotonia dystrophica, and hyperkalemic periodic paralysis (HyPP). This OMIA entry deals with Myotonia congentia. (FN thanks Izabela De Assis Rocha, who provided the basis of this contribution, working under the supervision of Professor Ernie Bailey; 15 April 2020)
Clin feat: From the case report described in a New Forest Pony by Wijnberg et al. (2012), the main clinical signs of myotonia congenita are the recurrent episodes of recumbency and difficulty to rise due to muscle stiffness. Occasionally, when the horse is stimulated, it seemed hyperreactive and temporary protrusion of the third eyelid occurred due to retraction of the eye uni- or bilaterally. It is important to note that this case report included only one affected foal. (FN thanks Izabela De Assis Rocha, who provided the basis of this contribution, working under the supervision of Professor Ernie Bailey; 15 April 2020)
Defect: yes
Prevalence: The occurrence of this variant in a wider sample of 42 additional New Forest ponies and 56 horses from 13 other breeds was consistent with it being causal of an autosomal recessive disorder in the New Forest breed: from the total 102 horses included in this study, Wijnberg et al (2012) found that the affected foal was the only homozygous C/C for the mutated allele 1775C, whereas its sire, its dam and seven other mares related to the foal were heterozygous A/C. All other horses here homozygous A/A for the wildtype allele 1775A.

Associated gene(s)

Derived from OMIA database dump (omia.xml, local); structured field, not verbatim prose. First-hand values below are verbatim substrings of the topic's pdf-raw/omia/<phene_id>.txt source file.

Gene: Entrez Gene ID 166568129 (no symbol in OMIA GeneSynonym) — OMIA Phene_Gene
OMIA molecular-genetics note: A gene defect in CLCN1 was then known to cause similar phenotypes in humans (see OMIM links above) and in goats (<a href="../../../../../../OMIA000698/9925/">OMIA 000698-9925</a> and in dogs (<a href="../../../../../../OMIA000698/9615/">OMIA 000698-9615</a>), which led Wijnberg et al (2012) to adopt a comparative candidate gene approach. By sequencing "all exons and several introns of the equine C…

Evidence (references)

Derived from OMIA database dump (omia.xml, local); structured field, not verbatim prose. First-hand values below are verbatim substrings of the topic's pdf-raw/omia/<phene_id>.txt source file.

1962. Myotonia in a horse. Science — PubMed:PMID13916691 — OMIA Phene_Article / Article
1987. A congenital form of myotonia with dystrophic changes in a quarterhorse. Equine Vet J — PubMed:PMID3622468 — OMIA Phene_Article / Article
1988. Progressive myotonia in foals resembling human dystrophia myotonica. Muscle Nerve — PubMed:PMID3398875 | DOI:10.1002/mus.880110403 — OMIA Phene_Article / Article
2012. A missense mutation in the skeletal muscle chloride channel 1 (CLCN1) as candidate causal mutation for congenital myotonia in a New Forest pony. Neuromuscul Disord — PubMed:PMID22197188 | DOI:10.1016/j.nmd.2011.10.001 — OMIA Phene_Article / Article
1987. Myotonia in man and animals: confusing comparisons. Equine Vet J — PubMed:PMID3622451 | DOI:10.1111/j.2042-3306.1987.tb01401.x — OMIA Phene_Article / Article
2014. Myotonic Disorders in Horses. MSD (Veterinary) Manual [https://www.msdvetmanual.com/musculoskeletal-system/myopathies-in-horses/myotonic-disorders-in-horses] — OMIA Phene_Article / Article
2022. Prevalence of genetic mutations in horses with muscle disease from a neuromuscular disease laboratory. J Equine Vet Sci — PubMed:PMID36150530 | DOI:10.1016/j.jevs.2022.104129 — OMIA Phene_Article / Article

Comparative medicine (human OMIM)

Derived from OMIA database dump (omia.xml, local); structured field, not verbatim prose. First-hand values below are verbatim substrings of the topic's pdf-raw/omia/<phene_id>.txt source file.

OMIM:160800 (type: trait) — OMIA Group_OMIM (via OMIA_ID)
OMIM:255700 (type: trait) — OMIA Group_OMIM (via OMIA_ID)
OMIM:118425 (type: gene) — OMIA Group_OMIM (via OMIA_ID)

New Forest Pony (Horse) — Myotonia (hereditary; OMIA-verified breed predisposition)