Syndactyly (mulefoot)

 

Gene: LRP4

Transmission: Autosomal, recessive (variable penetration)

For an autosomal recessive genetic disease an animal must have two copies of the mutation in question to be at risk of developing the disease.  Both parents of an affected animal must be carriers of at least one copy of the mutation.  Animals that have only one copy of the mutation are not at risk of developing the disease but are carrier animals that can pass the mutation on to future generations.

Mutations:

Mutation Holstein Friesian: Deletion, LRP4 gene; c.4863_4864 delAT, p.(Asp1621Gly1622 delLysCys), exon33, chromosome 15.

Mutation Angus: Substitution, (splicing error), LRP4 gene; intron37-38, chromosome 15.

Mutation Simmental: Substitution, LRP4 gene; c.3595 G>A, p.(Gly1199Ser), exon26, chromosome 15.

Mutation Simmental Charolais cross: Substitution, LRP4 gene; c.2719 Gly>Ala, p.(Gly907Arg), chromosome 15.

Breeds: Holstein, Angus, Simmental

Medical system: Skeletal

Age of onset of symptoms: From birth.

Syndactyly in the bovine, also known as mulefoot, is a congenital malformation affecting the structure of the limbs, resulting in abnormal fusion of the toes (uncloven hooves) reminiscent of a mule. Clinical signs mainly include bony fusion of the phalanges, most often affecting pair II. This anomaly is accompanied by marked curvature of the hooves and irregularities in the carpal bones. These malformations cause abnormal adaptation of the tendons and muscles, leading to significant locomotor difficulties. The condition is generally asymmetrical, affecting the forelimbs more severely. With age, complications such as premature hoof wear, joint pain, and impaired mobility occure, aggravating locomotor disorders.

Mulefoot, which has been reported in many breeds of cattle, follows autosomal recessive heredity with somewhat variable penetration.  It has been particularly problematic in the Holstein-Friesen breed, particularly with the advent of artificial insemination and embryo transfer techniques, due to a popular sire that was an acknowledged carrier of the causal mutation.  Furthermore, carrier female animals were shown to have elevated production of milk and buttermilk, conferring a production advantage to heterozygote cows.  DNA studies in the Holstein breed identified a mutation in the LRP4 gene as the cause of mulefoot, while studies of mulefoot seen in the Angus and Simmental breeds identified independent mutations within the same gene.  The LRP4 gene codes for the Low density lipoprotein receptor-related protein 4, which is involved in milk production but is also associated with embryonic development of the distal limb. DNA testing is available for the reported mutations, such that frequencies of mulefoot have been significantly reduced in susceptible breeds.

 

References:

OMIA link: [0963-9913]

Gozdek M, Mucha S, Prostek A, et al. (2024) Distribution of recessive genetic defect carriers in Holstein Friesian cattle: A polish perspective. Animals (Basel) 14:3170.  [pm/39595223]

Drögemüller C, Leeb T, Harlizius B, et al. (2007) Congenital syndactyly in cattle: four novel mutations in the low density lipoprotein receptor-related protein 4 gene (LRP4). BMC Genet 8:5. [pm/17319939]

Drögemüller C, Distl O. (2006) Genetic analysis of syndactyly in German Holstein cattle. Vet J 171:120-5. [pm/16427589]

Duchesne A, Gautier M, Chadi S, et al. (2007) Identification of a doublet missense substitution in the bovine LRP4 gene as a candidate causal mutation for syndactyly in Holstein cattle. Genomics 88:610-621. [pm/16859890]

Johnson EB, Steffen DJ, Lynch KW, Herz J. (2006) Defective splicing of Megf7/Lrp4, a regulator of distal limb development, in autosomal recessive mulefoot disease. Genomics 88:600-609.  [pm/16963222]

Leipold HW, Dennis SM, Huston K. (1973) Syndactyly in cattle. Veterinary Bulletin 43:399-403.

 

Contributed by: Flavie Cloutier and Lucie Hoang, Class of 2029, Faculté de médecine vétérinaire, Université de Montréal.  (Translation DWS)