UC Davis School of Veterinary Medicine Veterinary Genetics Laboratory
Pseudomyotonia (PMT) in Chianina & Romagnola Cattle
Introduction

Congenital pseudomyotonia (PMT) is a genetic defect that impairs muscle function. PMT is characterized by exercise-induced muscle cramping triggered when affected animals are startled or made to move faster than a slow walk. During cramping episodes, animals present uncoordinated gait, sometimes hopping on their back feet. During prolonged exercise, muscles become so stiff that animals fall over and are unable to stand. Cramping episodes cease and normal movement resumes when the stimulation is stopped. Clinical signs of PMT are present from birth and remain unchanged for life.

The abnormal muscle function in PMT cases results from mutations in the ATPase Sarcoplasmic/Endoplasmic Reticulum Ca2+ Transporting 1 (ATP2A1) gene. This gene encodes an enzyme required for calcium re-uptake by muscle cells and regulation of muscular contraction and relaxation. Three mutations have been identified in cattle that are associated with PMT.  These mutations result in amino acid substitutions in the ATP2A1 enzyme that reduce its activity and affect muscle relaxation. The Arg164His mutation (PCR) is found in Chianina and Romagnola breeds. Two linked mutations, [Gly211Val; Gly284Val] (PR), were also identified in Romagnola breed.

PMT is inherited as a recessive trait in cattle. This means that 2 copies of the defective gene are needed to cause the disease. In the Romagnola breed, the 2 defective genes can be of the same mutation ( PCR/PCR or PR/PR), or a combination of 2 mutations (PCR/PR). Males and females are equally affected.

The Veterinary Genetics Laboratory offers a test for PMT in Chianina and Romagnola breeds. Test results help breeders determine if a PMT mutation is present among breeding stock, and implement mating strategies to reduce incidence of PMT while retaining genetic diversity and other desirable attributes of these breeds. Carriers can be safely bred to N/N mates as this type of breeding will not produce affected calves.

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Results reported as:

N/N

Normal – no copies of PMT mutations are present.

N/PCR

Carrier – 1 copy of the PCR mutation is present. Animal is normal but can produce affected offspring if bred to another carrier.

N/PR

Carrier – 1 copy of the PR mutation is present. Animal is normal but can produce affected offspring if bred to another carrier.
PCR/PCR
Affected – 2 copies of the PCR mutation.
PR/PR
Affected – 2 copies of the PR mutation.
PCR/PR
Affected – 1 copy each of PCR and PR mutations.

References:
Murgiano L, Sacchetto R, Testoni S, Dorotea T, Mascarello F, Liguori R, Gentile A, Drögemüller C. Pseudomyotonia in Romagnola cattle caused by novel ATP2A1 mutations. BMC Vet Res. 2012 Oct 9; 8:186. doi: 10.1186/1746-6148-8-186.

Murgiano L, Testoni S, Drögemüller C, Bolcato M, Gentile A. Frequency of bovine congenital pseudomyotonia carriers in selected Italian Chianina sires. Vet J. 2013;195(2):238-40. doi: 10.1016/j.tvjl.2012.04.021.

Sacchetto R, Testoni S, Gentile A, Damiani E, Rossi M, Liguori R, Drögemüller C, Mascarello F. A defective SERCA1 protein is responsible for congenital pseudomyotonia in Chianina cattle. Am J Pathol. 2009 Feb;174(2):565-73. doi: 10.2353/ajpath.2009.080659.

Drögemüller C, Drögemüller M, Leeb T, Mascarello F, Testoni S, Rossi M, Gentile A, Damiani E. Identification of a missense mutation in the bovine ATP2A1 gene in congenital pseudomyotonia of Chianina cattle: an animal model of human Brody disease. Genomics. 2008 Dec;92(6):474-7. doi: 10.1016/j.ygeno.2008.

 
Veterinary Genetics Laboratory, Tel 530-752-2211, Email VGL