Analyses of Stage-Specific Multiple Forms of Lactate Dehydrogenase and of Cytochrome c during Spermatogenesis in the Mouse

Spermatogenesis is a programmed developmental process characterized by the inactivation of certain genes and the activation of other, testis-specific genes. Synthesis of unique gene products such as LDH-C₄ and cytochrome c_t occurs only at a precise stage of germ cell formation. The developmental sequences of gene activation for these proteins was observed by immunohistochemical procedures. LDH-C₄ is first detectable during mid-pachytene of the primary spermatocyte. The C subunits appear to be uniformly distributed throughout the cytoplasm of the spermatocyte. The mid-pachytene stage also marks the first appearance of cytochrome c_t. The association of this electron transport protein with spermatocyte mitochondria is reflected in a granular fluorescence of specific antibody-treated sections of testis. Neither the C subunit of LDH, nor cytochrome c_t appear in leptotene or early pachytene primary spermatocytes. These analyses indicate that there is stage-specific protein synthesis in the primary spermatocyte which is characterized by differential activation of the LDH-C locus and of the gene coding for cytochrome c_t.