Name: Miotonia Congénita - CM
Brand: Equigerminal
Price: 43.05 EUR

Sobre o teste

Teste de DNA para Miotonia Congénita (MC).

Este teste verifica a presença do gene recessivo MC.

Porquê testar?

Este teste genético ajuda os criadores a identificar cavalos portadores da mutação recessiva CM.

Podem ser feitas escolhas informadas para a seleção de reprodução e ajudar a prevenir o nascimento de poldros afetados.

Sinais clínicos

Signs are known from one affected foal, a colt that developed normally for the first four to six weeks of life and was examined at seven months.

Repeated episodes of going down and struggling to get back up because the muscles were too stiff, becoming more frequent over the months
More muscle than other foals of the same age
Very straight hind legs that barely bent at the hock, a stiff and unwilling way of going, hind feet that did not always follow the front ones, and easily losing balance
Fetlocks that could not be bent by hand, and a neck and body that could barely be moved
The eyeball pulling back into the socket, with the third eyelid sliding across for about thirty seconds after the eye was examined
Overreacting to anything sudden, such as the stable door opening
A changed voice: the whinny ended in a high squeak or a low growl
Bright and alert, weak but not uncoordinated; stiffness was the main problem

None of these signs is unique to congenital myotonia. Your veterinarian makes the diagnosis, using the history, the examination and this result.

Transmissão

Congenital myotonia is recessive. A foal needs one copy from the sire and one from the dam to be affected. The gene is not on a sex chromosome, so colts and fillies are affected equally.

What each mating can produce:

n/n x n/n gives 100% n/n
n/n x n/CM gives 50% n/n, 50% n/CM
n/n x CM/CM gives 100% n/CM
n/CM x n/CM gives 25% n/n, 50% n/CM, 25% CM/CM
n/CM x CM/CM gives 50% n/CM, 50% CM/CM
CM/CM x CM/CM gives 100% CM/CM

Prevenção

There is no cure, so prevention is a breeding decision.

Breeding. Never mate two carriers. Mate a carrier only with a partner that tested negative, and test every foal. No affected foals are born, though some foals will be carriers. This keeps a valuable line while the variant is bred out. Check your studbook's current rules before registering or licensing a stallion.

Managing an affected pony. No treatment has been evaluated in the horse. Your veterinarian guides care case by case.

Descrição dos resultados

O teste de DNA verifica a presença do gene recessivo cm e apresenta os resultados como um dos seguintes:

N/ - Normal para Miotonia Congénita (CM). Ausência da variante afetada responsável pela Miotonia Congénita
N/cm - Portador de Miotonia Congénita (CM). Presença de uma cópia da variante genética causadora da Miotonia Congénita. O cavalo é clinicamente saudável e pode transmitir a variante genética responsável pela CM a 50% da sua descendência quando reproduzido.
cm/ - Afetado pela CM. Presença de duas cópias da variante genética causadora da Miotonia Congénita. O cavalo está afetado pela Miotonia Congénita e transmitirá a variante genética a 100% da sua descendência.

Requisitos da amostra

30 a 40 raízes de crinas ou 5 mL de sangue num tubo K3 EDTA

Envie a sua amostra por correio normal para:

Equigerminal Lab HIESE
Rua da Quinta do Sobreiro Nº25
3230-343 Penela, Portugal

Tempo de resposta

Processamento padrão: resultados no prazo de 5 a 10 dias úteis após a chegada da amostra ao laboratório. O envio é organizado e pago pelo cliente, e o tempo de transporte não está incluído nos 5 a 10 dias úteis.

As amostras que falhem a extração ou a amplificação de ADN são repetidas sem custo adicional, o que pode acrescentar alguns dias úteis. Contactamo-lo se for necessária uma nova amostra.

Como funciona

🛒 Compre o teste: selecione e compre o teste online.

📧 Receba as instruções: após a confirmação do pagamento, recebe por email as instruções de recolha da amostra.

✨ Recolha a amostra: arranque 20 a 40 raízes de pelo com o bolbo, ou peça ao seu veterinário que colha sangue num tubo K3-EDTA.

📄 Preencha o formulário: imprima e preencha o formulário de submissão com a identificação do animal.

📮 Envie para o laboratório: Equigerminal, S.A., HIESE, Rua da Quinta do Sobreiro, 25, Quinta Vale do Espinhal, 3230-343 Penela, PORTUGAL.

📄 Receba o relatório: o relatório certificado é emitido assim que a análise for validada.

FAQs

At what age can a pony be tested?
Any age, from newborn foal to adult. The genotype never changes, so one test lasts for life.

How certain is this variant?
It rests on a single published case. The affected foal had two copies and its sire and dam one each. The authors call it a probable cause that matched the condition in every animal studied.

Is it fatal?
The published report gives no outcome, survival figures or prognosis, so no one can say that it is. What it means for an individual pony is a veterinary judgement.

Does a negative result mean my pony cannot get stiff muscles?
No. This test looks only for congenital myotonia. Hyperkalaemic periodic paralysis is a separate condition with its own test, and horses have other muscle diseases with no known gene.

For Professionals

Genetic and clinical detail for veterinarians, geneticists and laboratories.

Gene / locus: CLCN1 (chloride voltage-gated channel 1, skeletal muscle), ECA4.
Variant: D592A (Asp592Ala), missense at a residue conserved across mammals, predicted probably damaging; candidate causal variant (Wijnberg et al., 2012). HGVS (EquCab3.0): NC_009147.3:g.96518592A>C; XM_001915636.4:c.1775A>C; XP_001915671.3:p.(Asp592Ala).
Alternative designations: published against GenBank XM_001915636 / XP_001915671 (same numbering as the current RefSeq versions).
Variant identifiers: rs5334475185 (EVA); OMIA variant 161.
Variant classification: not currently evaluated (ISAG/AVCG, per OMIA).
Mechanism: the CLCN1 chloride channel provides most of the resting membrane conductance of the muscle fibre; reduced channel function leaves the fibre firing after contraction, producing myotonia. Human homologue: myotonia congenita; the same gene underlies myotonia in goats, mice and dogs.
Variant analysis: three CLCN1 differences were found; two did not segregate with disease and are unlikely to alter protein function. The full-length cDNA of the affected foal showed no other abnormality, which excludes a splicing effect (Wijnberg et al., 2012).
Inheritance: autosomal recessive (OMIA code R).
Penetrance / expressivity: heterozygous relatives were unaffected (Wijnberg et al., 2012).
Breeds with documented carriers or cases: New Forest Pony only (OMIA variant record); absent in 56 horses of 13 other breeds (Wijnberg et al., 2012).
Allele / carrier frequencies: no population survey published. In the discovery study (102 animals: affected foal, dam, sire, 22 relatives, 21 unrelated New Forest Ponies, 56 horses of 13 other breeds), the affected foal was the only homozygote and 9 carriers were found, all within one family: eight mares including the dam, and the sire. All traced to one suspected founder stallion, paternal grandsire and maternal great-grandsire of the affected foal; none of the 21 unrelated New Forest Ponies carried it. The authors suggest the variant may be recent and confined to one line (Wijnberg et al., 2012). Not detected in 296 horses with muscle disease tested at a neuromuscular laboratory (Aleman et al., 2022). Family-derived percentages are not breed carrier rates.
Clinical / diagnostic notes for veterinarians: in the index case (Utrecht University equine clinic), electromyography showed myotonic discharges in every muscle tested; biopsies of four muscles showed marked variation in fibre diameter without necrosis; hyponatraemia, hypokalaemia, hypomagnesaemia and hypochloraemia with raised calcium and phosphate normalised after an episode; renal function was normal; HYPP genotype was negative. The myotonic EMG pattern is not specific to this disease. Electromyography and muscle biopsy are separate procedures and are not replaced by this test. The discovery authors state that direct genetic testing enables eradication of the disease from the New Forest pony breeding population.

Key references:

Wijnberg ID, Owczarek-Lipska M, Sacchetto R, Mascarello F, Pascoli F, Grunberg W, van der Kolk JH, Drogemuller C (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 22:361-367. doi:10.1016/j.nmd.2011.10.001. PMID 22197188.
Aleman M, Scalco R, Malvick J, Grahn RA, True A, Bellone RR (2022). Prevalence of genetic mutations in horses with muscle disease from a neuromuscular disease laboratory. J Equine Vet Sci 118:104129. doi:10.1016/j.jevs.2022.104129.