Congenital Idiopathic Megaesophagus (CIM) - German Shepherd Type

Acronym:	CIM
Gene:	MCHR2
Mutation:	g.58117748-58117813
Inheritance:	Complex mode of inheritance
Sample type:	CHS (Cheek Swab), WBE (Whole Blood EDTA)

Genetics and characteristics

Congenital idiopathic megaesophagus (CIM) is a genetic gastrointestinal disorder of the esophagus in dogs. CIM is characterized by dilation of the esophagus and decreased peristalsis with the highest disease incidence in the German shepherd dog (GSD). Symptoms of CIM develop early in puppies and include regurgitation of meals and water, weight loss, coughing and other breathing complications. CIM in GSD species is a consequence of a repetitive sequence located in or upstream of Melanin-Concentrating Hormone Receptor 2 (MCHR2) on chromosome 12. The repetitive sequence in MCHR2 gene correlates with MCHR2 expression and imbalance of melanin-concentrating hormone which is associated with CIM development.

This type of a motility disorder of the esophagus is inherited in a complex manner. Across dogs and wolves, the most common gene variant includes two copies of the repeat, whereas the predominant gene variant in GSDs has one or three copies. The single-copy gene variant is strongly associated with CIM. Dogs who have two single-copy gene variants are most likely to develop the disease. Even though the both sexes are predisposed to develop the disease, male GSDs are two times more affected then females. Early genetic testing can help identify the GSD that carry the high risk gene variants and prevent further breeding.

  

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 Results Reported As

 

 

 

 

 

 

 

 

 

 

  

 

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References:

Bell SM, Evans JM, Evans KM, Tsai KL, Noorai RE, Famula TR, Holle DM, Clark LA. (2022) Congenital idiopathic megaesophagus in the German shepherd dog is a sex-differentiated trait and is associated with an intronic variable number tandem repeat in Melanin-Concentrating Hormone Receptor 2. PLoS Genet. 18(3):e1010044. doi: 10.1371/journal.pgen.1010044. PMID: 35271580; PMCID: PMC8912139.

Mace S, Shelton GD, Eddlestone S. (2012) Megaesophagus. Compend Contin Educ Vet. 34(2):E1. PMID: 22488663.