Submission Number: GER-4-323-141

Abstract Number: 2

ROLES OF GAP JUNCTIONAL COMMUNICATION IN GAMETOGENESIS REVEALED BY GENE TARGETING.

Cheryl L Ackert* ², Wendi A Redgrift ¹, Marilyn J O'Brien ², John J Eppig* ², Kevin J Barr ¹, David K Pomerantz* ¹ and Gerald M Kidder* ¹

Department of Physiology, The University of Western Ontario, London, Ontario ¹
The Jackson Laboratory, Bar Harbor, Maine ²

Abstract:
The connexins are a large family of gap junction subunit proteins, many of which have been implicated in human disease. Gap junctions are present in almost all tissues of the body where they provide intercellular channels for direct transfer of small molecules from cell to cell. We have characterized the effects of a targeted mutation in the gene encoding mouse connexin43 (Cx43), a gap junction protein that is expressed in multiple organs, including the gonads. The ovarian follicle is a functional syncytium, with the somatic (granulosa) cells being coupled via gap junctions containing Cx43. In the testis, Cx43 gap junctions couple Sertoli cells with each other and Leydig cells with each other, and may couple spermatogonia with Sertoli cells. In order to assess the importance of Cx43 gap junctions for gametogenesis, we grafted gonads from late gestation fetuses lacking Cx43 (which die at birth due to a cardiac defect) into the kidney capsules of immunocompromised SCID mice, and allowed them to develop for up to four weeks. By the end of the graft period, tertiary (antral) follicles had developed in normal (wild-type or heterozygote) ovaries but follicles in mutant ovaries failed to develop beyond the primary (unilaminar) stage, indicating that coupling between granulosa cells mediated by Cx43 is required for their continued proliferation. The oocytes developing within the mutant follicles were also affected: their growth was retarded, they were morphologically abnormal, and they could not be fertilized. Grafted wild-type or heterozygote testes likewise appeared histologically normal, but mutant testes were almost devoid of germ cells, as though postnatal survival and/or proliferation of the spermatogonia had been impaired. Thus gametogenesis is disrupted in mice of both sexes when Cx43 is lacking. We conclude that gap junctional coupling via Cx43-containing intercellular channels is an important factor in gonadal development and fertility. Supported by NSERC and MRC of Canada.

Keywords: mouse, folliculogenesis, granulosa cells, oocyte, connexin, spermatogonia, Sertoli cells, spermatogenesis, oogenesis

This abstract is being presented at: 11:00 AM in session:
Minisymposium XV: GAP JUNCTIONAL COMMUNICATION IN REPRODUCTION