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Connexin 33: A Rodent-Specific Member of the Gap Junction Protein Family?

LUTZ KONRAD

SABINE KLIESCH

RAINER M. BOHLE

From the ^* Department of Veterinary Anatomy, Histology and Embryology, University of Giessen, Germany; the Department of Urology, University of Marburg, Germany; the Clinic and Polyclinic of Urology, University of Muenster, Germany; and the Institute of Pathology, University of Giessen, Germany.

Correspondence to: Prof Dr Martin Bergmann, Justus-Liebig-Universität, Institut für Veterinär-Anatomie, -Histologie und -Embryologie, Frankfurter Straße 98, D-35392 Giessen, Germany (e-mail: Martin.Bergmann{at}vetmed.uni-giessen.de).

Gap junctional intercellular communication between Sertoli cells and between Sertoli cells and spermatogonia is considered to play a key role in the regulation of both proliferation and differentiation of germ cells. A member of the gap junction protein family, Connexin 33 (cx33), probably has an inhibitory effect on the formation of gap junctions and so far it is the only cx that has been exclusively found in rat and mouse testes. Thus, this connexin seems to be a special member of the cx family. Using immunohistochemistry, Western blot analysis, polymerase chain reaction, and reverse transcription (RT)-PCR (tissue homogenate and microdissected cells), we studied the possible occurrence of cx33 at the protein, the DNA, and the RNA level in human testis. Whereas immunohistochemistry using the only commercially available anti-cx33 antibody showed similar labeling to the rat within the seminiferous epithelium, we could not find any further evidence for the existence of cx33 using Western blot analysis, PCR, and RT-PCR in human testis. Based on the demonstration of the staining pattern of mitochondria in human germ cells and on preabsorption studies, we could demonstrate anti-cx33 antibody cross-reacting with mitochondrial ferritin, a protein localized in the mitochondria of human testicular spermatids. Therefore, we were not able to abide by the suspicion that cx33 is present in human testis. Additionally, it was not possible to demonstrate cx33 via PCR and immunohistochemistry in the testis of different mammals (dog, cattle, pig, horse, and marmoset monkey) with normal spermatogenesis. These data indicate that cx33 seems to be the first rodent-specific testicular cx.

     Key words: Gap junctional intercellular communication, cx33, testis, spermatogenesis

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