Robertsonian translocation

From Dog

Robertsonian translocation is a rare autosomal-dominant genetic chromosomal aberration of female dogs characterized by only 77 chromosomes (normally 78), ambiguous external genitalia and infertility[1].

A breed predisposition has been reported in the Poodle[2], Boxer[3], Bernese Mountain Dog[4], West Highland White Terrier[5] and Treeing Walker Coonhound[6].

Robertsonian translocation involves the centric fusion of two acrocentric chromosomes, usually involving chromosome 23, and is the most common chromosomal translocation reported in dogs.

Affected bitches usually present with female-to-male sex reversal, with 2 normal X chromosomes and a lack of a number of Y chromosome-linked genes. Although female genitalia may be present, vulvar narrowing and clitoral hypertrophy is usually evident, as well as the presence of testes or ovotestes. Spontaneous, first-trimester abortions, frequently reported in humans[7], does not appear to occur in canine patients.

Infertility is usually a feature of this condition, but heterozygous carriers may still be fertile and produce normal offspring.

Diagnosis requires DNA testing, using cytogenetic analyses with the use of Giemsa staining.

A differential diagnosis would include hermaphroditism and Trisomy X.

Affected dogs are usually healthy and live a good quality of life.

References

  1. Larsen RE et al (1979) Breeding studies reveal segregation of a canine Robertsonian translocation along Mendelian proportions. Cytogenet Cell Genet 24(2):95-101
  2. Mayr B et al (1986) A new type of Robertsonian translocation in the domestic dog. J Hered 77(2):127
  3. Nolte M et al (1993) Different cytogenetic findings in two clinically similar leukaemic dogs. J Comp Pathol 108(4):337-342
  4. Switonski M et al (2011) Robertsonian translocation in a sex reversal dog (XX, SRY negative) may indicate that the causative mutation for this intersexuality syndrome resides on canine chromosome 23 (CFA23). Sex Dev 5(3):141-146
  5. Switonski M et al (2003) Robertsonian translocation (8;14) in an infertile bitch (Canis familiaris). J Appl Genet 44(4):525-527
  6. Stone DM et al (1991) A novel Robertsonian translocation in a family of Walker hounds. Genome 34(4):677-680
  7. Kolgeci S et al (2012) Recurrent abortions and down syndrome resulting from Robertsonian translocation 21q; 21q. Med Arh 66(5):350-352