Vn. Meyerswallen et al., MULLERIAN-INHIBITING SUBSTANCE IS PRESENT IN EMBRYONIC TESTES OF DOGSWITH PERSISTENT MULLERIAN DUCT SYNDROME, Biology of reproduction, 48(6), 1993, pp. 1410-1418
Mullerian Inhibiting Substance (MIS) causes regression of the Mulleria
n ducts during a critical period in embryonic development in male mamm
als. In Persistent Mullerian Duct Syndrome (PMDS), an autosomal recess
ive trait in humans and dogs, the Mullerian ducts fail to regress in o
therwise normal males. Previously we reported that PMDS-affected dogs
produce bioactive testicular MIS postnatally. The purpose of the prese
nt study was to determine whether PMDS-affected canine embryos appropr
iately express MIS mRNA and protein during the critical period for Mul
lerian duct regression. Homozygous (PMDS-affected) and normal canine e
mbryos were removed from timed pregnancies. Gonadal sex and the degree
of Mullerian duct regression were determined from histologic sections
. Positive immunohistochemical staining for MIS was found in testis se
ctions of PMDS-affected and normal male embryos. A 1.8-kb MIS mRNA tra
nscript was detected in testes of PMDS-affected males and normal male
embryos and neonates. Furthermore, equal amounts of MIS mRNA transcrip
t were detected in testes of PMDS-affected embryos and normal male lit
termates during the critical period for Mullerian duct regression. The
se data support a hypothesis of target organ resistance, such as an ab
normality in the putative MIS receptor, as the etiology of the defect
in this dog model.