Wolffian duct, determination

In the X-linked Tfm mutation of mice, which present an external female phenotype but without internal Mullerian or Wolffian duct-derived organs, the demonstrable levels of androgen receptors as determined by DHT binding are extremely low in kidney (79-81) and brain (82). Whether the tiny residual quantities of androgen receptor merely represent very limited expression of a normal X-linked androgen receptor gene, or alternatively the formation of some mutationally altered receptor protein with diminished steroid-binding capacity, cannot be decided from the limited data available (26). 

The differentiation of the sex organs of males or females from indifferent pri-mordia is demonstrated in Fig. 89 (Jost, 1961). The differentiation of the genital tract occurs after the differentiation of gonads. Hormonal concentrations determine the character of development. At the present time it is known that the development of female sex structures in mammalian embryos does not require sex hormones or ovaries. In contrast, the male genitals develop under the influence of male sex hormones. These determine the differentiation of the Wolffian duct and the reduction of Muller s ducts (Witschi, 1967 Levina, 1974). 

Ohno (1971) suggested that this system is the basis for sex detennination in mammals (Fig. 91) and includes two gene regulators. One of these determines the development of indifferent gonads in the testis or ovary direction and another controls the formation of secondary sex characteristics. The expression of the male or female phenotype depends upon the presence or absence of testosterone. Mullerian ducts are differentiated into fallopian tubes and the uterus, and Wolffian ducts are reduced if XY embryos are castrated before the critical period in development. Testosterone injection into XY and XX embryos stimulates development of Wolffian ducts into seminal ducts, epididymis and seminal vesicles and determines the differentiation of the urogenital sinus into the prostate and penis. However, in this experiment the total reduction of Mullerian tubes was not obtained and the castrated embryos demonstrated the hermaphroditic phenotype. It is possible that Mullerian tube degeneration is caused by the presence of another male hormone... 

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