Role of Deoxyribonucleic Acid Polymerase ε in Spermatogenesis in Mice1

Abstract

Previous studies on DNA polymerase epsilon indicate that this enzyme is involved in replication of chromosomal DNA. In this study, we examined the expression of DNA polymerases alpha, delta, and epsilon during mouse testis development and germ cell differentiation. The steady-state levels of mRNAs encoding DNA polymerase epsilon and the recombination enzyme Rad51 remained constant during testis development, whereas the mRNA levels of DNA polymerases alpha and delta declined from birth until sexual maturity. Immunohistochemical staining methods, using a stage-specific model of the seminiferous epithelium, revealed dramatic differences between DNA polymerase alpha and epsilon distribution. As expected, DNA polymerase alpha and proliferating cell nuclear antigen showed relatively strong immunostaining in mitotically proliferating spermatogonia and even stronger staining in preleptotene cells undergoing meiotic DNA replication. The distribution of Rad51 was similar, but there was a dramatic peak in late pachytene cells. In contrast, DNA polymerase epsilon was detectable in mitotically proliferating spermatogonia but not in the early stages of meiotic prophase. However, DNA polymerase epsilon reappeared in late pachytene cells and remained through the two meiotic divisions, and was present in haploid spermatids up to the stage at which the flagellum starts developing. Overall, the results suggest that DNA polymerase epsilon functions in mitotic replication, in the completion of recombination in late pachytene cells, and in repair of DNA damage in round spermatids. In contrast, DNA polymerases alpha and delta appear to be involved in meiotic DNA synthesis, which occurs early in meiotic prophase, in addition to functioning in DNA replication in proliferating spermatogonia.

KIN17 encodes an RNA-binding protein and is expressed during mouse spermatogenesis

“…Haploid cells lacked detectable PCNA reactivity as well as Sertoli cells (not shown) in agreement with published observations (Kamel et al, 1997). Negative control sections where primary antibody was replaced by mouse IgG remained unstained ( Fig.…”

Dexrazoxane exacerbates doxorubicin-induced testicular toxicity

“…PCNA, involved in DNA replication and repair, also prominently expressed in the nuclei of spermatogonia and primary spermatocytes (Chapman & Wolgemuth 1994, Kamel et al 1997, Steger et al 1998, Bar-Shira Maymon et al 2003. DAZL that stains intermediate and B type spermatogonia as well as preleptotene and pachytene spermatocytes (Saunders et al 2003).…”

Slipping while sleeping? Trinucleotide repeat expansions in germ cells

“…Mitotic and DNA metabolic activities change throughout the stages of gametogenesis (Figure 1b). Many replication, repair or recombination genes show altered or specialized expression during gametogenesis [4][5][6][7][8][9]. If expansions occur during replication, the larger number of mitotic divisions in male gametogenesis could explain the paternal bias for HD mutation.…”

“…Mouse-strain-specific differences might also account for variable murine mutation patterns: unsuspected mutations in repair genes within the supposed wild-type embryonic stem cells, such as those occurring in the polymerase iota (pol i) gene in the 129-derived strains [18], might unknowingly contribute to repeat instability. Importantly, high levels of the error-prone DNA polymerases i, k, l, h and b, as well as pol e, are present in mouse testes at various stages of spermatogenesis, before, during and after meiosis, and, in some cases, in round spermatids ( [8,9] and Refs therein). Outside of mitotic spermatogonia, the replicative polymerases a and d are present at higher levels coincident with meiotic DNA synthesis ( [8] and Refs therein).…”

“…Importantly, high levels of the error-prone DNA polymerases i, k, l, h and b, as well as pol e, are present in mouse testes at various stages of spermatogenesis, before, during and after meiosis, and, in some cases, in round spermatids ( [8,9] and Refs therein). Outside of mitotic spermatogonia, the replicative polymerases a and d are present at higher levels coincident with meiotic DNA synthesis ( [8] and Refs therein). Strain-specific defects in polymerases or other repair genes might influence the interpretation of transmitted or somatic instabilities observed in transgenic mice.…”