PARENT SESSION

(102) EXPRESSION OF THE LADYBIRD-LIKE HOMEOBOX 2 (LBX2) FACTOR DURING MOUSE TESTICULAR AND EPIDIDYMAL DEVELOPMENT.

Moisan, Vanessa¹, Bomgardner, Daniela³, Tremblay, Jacques ^{1, 2}, ¹ CHUL Research Centre, Ste-Foy, QC, Canada³ University of Virginia, Charlottesville, VA² Université Laval, Ste-Foy, QC, Canada

ABSTRACT- Homeoproteins are transcription factors that regulate gene expression in several critical processes such as development, organogenesis, and cell differentiation in many species. They have been detected in every tissue studied so far and the male reproductive system is no exception. Indeed, through a degenerate PCR approach, we have recently detected several homeoproteins in the male reproductive system. One of the homeobox transcription factors that we have identified is the ladybird-like homeobox 2 (Lbx2). We previously showed that Lbx2 was expressed in a region-specific manner in the adult mouse epididymis. We now report the results of a detailed analysis of Lbx2 expression during testicular and epididymal development. Non-isotopic in situ hybridization was performed on 5m sections of mouse testis and epididymis prepared from seven developmental stages: embryonic day 14 (E14), E18, postnatal day 1 (P1), P5, P21, P34, and P70. We found that Lbx2 was expressed in both tissues throughout development. At E14, Lbx2 was detected in cells of the mesonephros, in the mesonephric tubules (which give rise to the efferent ducts), and in cells of the developing Wolffian duct (which will develop into the epididymis, vas deferens, and seminal vesicles). Later during development, Lbx2 was indeed found in the principal and basal cells of the epididymis and in the vas deferens. In the testis, Lbx2 was strongly expressed in Sertoli cells as early as E14 and its expression remained high in theses cells throughout development. Lbx2 was also detected in interstitial Leydig cells but its expression was transient. Indeed, during fetal life, Lbx2 was expressed at E18 only, whereas in postnatal life, occasional labeling was detected in Leydig cells at the onset of puberty (P34). Lbx2 could not be detected in Leydig cells from adult animals (either by in situ hybridization or RT-PCR). Germ cells appeared negative at all time. In summary, we have identified and characterized the expression of a novel homeoprotein, Lbx2, during development of the male reproductive system and found that it is expressed in a cell- and temporal-specific manner. Thus our results suggest a role for Lbx2 in male reproductive system development and function. Supported by CIHR.

KEY WORDS: homeoprotein, epididymis, testis, development