The Expression Patterns of Connexin Isoforms in the Rat Caput Epididymis During Postnatal Development

Abstract

Intercellular interactions are important for the proper development and regulation of tissue function. This is especially necessary in the epididymis, a part of male reproductive tract where sperm become mature and acquire their fertilizing capacity. The caput region of the epididymis consists of several types of cells, including principal, basal, and apical cells. Direct intercellular communication is thus required to precisely regulate the functions of the caput epididymis. In this regard, connexin (Cx) is a molecule that forms channels, which allow the direct exchange of small molecules between cells, enabling intercellular communication. In this study, the expression of Cx isoforms in the caput epididymis at different postnatal ages was determined by using quantitative real-time polymerase chain reaction analysis. Nine of 13 Cx isoforms were detected. The transcript levels of Cx30.3, 31, 31.1, 32, and 40 were highest at 45 days of age, while the expression of Cx43 and 45 gradually decreased with age. A substantial fluctuation of Cx26 expression was detected, with significant decreases before and during puberty, followed by a transient increase at adult-hood and rapid decreases at an old age. A significant increase in Cx37 transcript was observed at 25 days of age, followed by gradual decreases at adult and old ages. These results indicate the significant differential expression of various Cx isoforms in the caput epididymis during postnatal development. It further suggests that the functional regulation and developmental maturation of the caput epididymis are highly related to the postnatal age-related differential expression of Cx isoforms.

Differential Expression of Multiple Connexins in Rat Corpus and Cauda Epididymis at Various Postnatal Stages

“…Expression patterns of some Cx genes in the epididymis during the first 3 months of the postnatal period were examined by Dufresne et al (2003). Similar to our current and previous findings (Han and Lee, 2013), they reported differential expression patterns of Cx26, Cx31.1, Cx32, and Cx43 between the head of the epididymis and the cauda epididymis . However, Dufresne et al (2003) used a mixed tissue sample of IS and caput and corpus epididymis to determine the expression of Cx genes in the head of the epididymis.…”

“…Expression of some Cx genes was found to be relatively higher at neonatal and prepubertal ages than at adult and old ages, while other Cx genes were strongly expressed during adult and old age. Interestingly, the types of Cxs expressed in the caput epididymis were the same as those found in the corpus and cauda epididymis (Han and Lee, 2013). However, the expression of Cx26 was not observed in the IS (Seo et al, 2010), implying functional discrimination between the IS and the rest of the epididymis.…”

“…Our previous study showed differential expression of Cx genes in the rat epididymis from 1 week of age to 2 years of age (Han and Lee, 2013). In the present study, expressional patterns of Cxs in the corpus and caudal epididymis of rat were investigated by quantitative real-time PCR analyses while paying careful attention to differences in the expression of Cx genes among epididymal regions.…”

“…The seminal vesicle expresses Cx32 mRNA (Meda et al, 1993), and the prostate possesses transcripts of Cx26, Cx32, and Cx43 (Pointis et al, 2005). The presence of several Cxs transcripts in the epididymis has been evaluated in previous studies (Cry, 2011;Han and Lee, 2013). These Cxs include Cx26, Cx30.3,Cx31,Cx31.1,Cx32,Cx37,Cx40,Cx43,and Cx45. Comparison analyses of Cx genes expression between the head and tail part of the epididymis from 7 to 91 days of postnatal age conducted by Dufresne et al (2003) demonstrated segmental-specific and postnatal age-differentiated expression patterns of Cx genes in the epididymis.…”

“…Because the head of the epididymis used in Dufresne's research includes the IS, caput epididymis, and corpus epididymis, it is difficult to determine whether their findings truly represent segmentspecific expression of Cx genes. Indeed, our previous studies demonstrated that expression of Cx genes between the IS and caput epididymis are not identical (Han and Lee, 2013;Seo et al, 2010). Therefore, more careful examination of the expression of Cx genes in each epididymal segment is required to determine the actual segment-specific expression of Cx genes in the epididymis.…”