I. Abnormalities in cells of the testis, efferent ducts, and epididymis injuvenile and adult mice with beta-hexosaminidase A and B deficiency

beta-Hexosaminidase (Hex) is a lysosomal enzyme that exists as two major is oenzymes: Hex A (subunit structure, alpha beta) and Hex B (beta beta) The p resence of Hex in the testis and epididymis suggests important roles for th e enzyme and its substrates in male fertility and reproductive functions. D isruption of the Herb gene encoding the beta-subunit of Hex has led to the generation of a mouse model of human Sandhoff disease that survives to adul thood, enabling us to analyze the effects of Hex A and Hex B deficiency on epithelial cellular morphology of the male reproductive tract. At 1 and 3 m onths of age, the testes, efferent ducts, and epididymides of Hex-deficient (Hexb -/-) and wild-type (Hexb +/+) mice were perfuse fixed and analyzed b y routine light and electron microscopy (LM and EM, respectively) as well a s with immunocytochemistry employing antibodies to lysosomal proteins. In t he testis, the morphological appearance and topographical arrangement of th e cell types of the seminiferous epithelium of Herb -/- mice were similar t o those of wild-type animals at both ages. Both Sertoli and germ cells appe ared to be unaffected. However, at both ages, myoid cells and macrophages s howed an increased number of lysosomes in their cytoplasm as compared with the number seen in controls. The epithelial cells of the efferent ducts als o showed an accumulation of lysosomes that increased with age as compared w ith controls. Principal cells of the entire epididymis revealed an increase in the size and number of lysosomes at 1 month of age as compared with tho se of controls, and by 3 months, these lysosomes often filled the supranucl ear and basal regions of the cells. Narrow cells of the distal initial segm ent and intermediate zone, normally slender cells showing several lysosomes , became greatly enlarged and entirely filled with lysosomes in Herb -/- mi ce. Clear cells of the caput, corpus, and cauda regions also showed a progr essive increase in the size and number of lysosomes with age as compared wi th controls; the clear cells of the mutant mice were often enlarged and at times bulged into the lumen. Some basal cells of each epididymal region in Herb -/- mice were similar to controls at 1 and 3 months, showing few lysos omes, while others showed an accumulation of lysosomes. Lysosomes of all af fected epithelial cells were of varying sizes, but many large ones were pre sent, apparently resulting from lysosomal fusion. Although pale stained, th eir identification as lysosomes was confirmed by EM immunocytochemistry wit h anti-cathepsin D and anti-Hex A antibodies. Predominantly in the proximal initial segment, large, pale cellular aggregates were noted in the LM anal ysis at the base of the epithelium, which by EM analysis were identified as belonging to two different cell types, narrow cells and halo cells. Taken together, these data reveal an increase in the size and number of lysosomes in all epithelial cell types lining the efferent ducts and entire epididym is as well as in myoid cells and macrophages of the testis. In the light of data showing epididymal defects restricted predominantly to the initial se gment in Hexa -/- (Hex A-deficient) mice, our data on the Herb -/- mice dem onstrate a major role for Hex that can be fulfilled by either Hex A or Hex B in the epididymis.