Failure of spermatogenesis in mouse lines deficient in the Na+-K+-2Cl– cotransporter
Amy J. Pace, Eddie Lee, Krairek Athirakul, Thomas M. Coffman, Deborah A. O’Brien, Beverly H. Koller
Amy J. Pace, Eddie Lee, Krairek Athirakul, Thomas M. Coffman, Deborah A. O’Brien, Beverly H. Koller
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Failure of spermatogenesis in mouse lines deficient in the Na+-K+-2Cl– cotransporter

Abstract

The Na+-K+-2Cl– cotransporter (NKCC1) carries 1 molecule of Na+ and K+ along with 2 molecules of Cl– across the cell membrane. It is expressed in a broad spectrum of tissues and has been implicated in cell volume regulation and in ion transport by secretory epithelial tissue. However, the specific contribution of NKCC1 to the physiology of the various organ systems is largely undefined. We have generated mouse lines carrying either of 2 mutant alleles of the Slc12a2 gene, which encodes this cotransporter: a null allele and a mutation that results in deletion of 72 amino acids of the cytoplasmic domain. Both NKCC1-deficient mouse lines show behavioral abnormalities characteristic of mice with inner ear defects. Male NKCC1-deficient mice are infertile because of defective spermatogenesis, as shown by the absence of spermatozoa in histological sections of their epididymides and the small number of spermatids in their testes. Consistent with this observation, we show that Slc12a2 is expressed in Sertoli cells, pachytene spermatocytes, and round spermatids isolated from wild-type animals. Our results indicate a critical role for NKCC1-mediated ion transport in spermatogenesis and suggest that the cytoplasmic domain of NKCC1 is essential in the normal functioning of this protein.

Authors

Amy J. Pace, Eddie Lee, Krairek Athirakul, Thomas M. Coffman, Deborah A. O’Brien, Beverly H. Koller

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Histological analysis of the reproductive tract of wild type (a–d) and N...
Histological analysis of the reproductive tract of wild type (a–d) and NKCC1-deficient (e–h) animals. Representative sections are from Slc12a2–/– animals, although the defect in both NKCC1-deficient lines is identical. Sections through the cauda epididymis of both normal (a) and Slc12a2–/– (e) mice show columnar epithelium with stereocilia on the apical surface. In wild-type mice the epididymal lumen is filled with mature sperm. In contrast, no sperm are observed in NKCC1-deficient animals, and the epididymal lumen is filled with PAS-staining material and occasional cells with pyknotic nuclei (arrow, e). Bars, 50 μm. Sections through the testes of Slc12a2–/– (f) and wild-type (b) males show a decrease in the size of the seminiferous tubules, resulting from a variable loss of germ cells from the seminiferous epithelium. Multinucleated cells are often seen in the lumens of the seminiferous tubules of the NKCC1-deficient males (arrows, f). Bars, 100 μm. High-magnification photomicrographs of the seminiferous tubules of normal animals (c, d) show tubules containing developing germ cells at all stages of spermatogenesis. This includes early spermatocytes (arrow, d), elongating spermatids (arrow, c), and later condensed spermatids (d) near the lumen, identified by their PAS-staining acrosomes. Comparable photomicrographs of Slc12a2–/– animals (g, h) show that the number of spermatids is substantially reduced. A small number of developing spermatids with PAS-stained acrosomes can be identified (arrows, g). Normal Sertoli cells were observed (s in h) along the basement membrane of the seminiferous epithelium, as well as spermatogonia and/or early spermatocytes (e in h) and a reduced number of large pachytene spermatocytes (p in h). In c, d, g, and h, bars, 30 μm.