High impact information on Gjb3

• Within the connexin family, these two proteins are most closely related to one another (70% amino acid sequence identity) and to Cx31 (65 and 68% identity, respectively) [1].
• Undifferentiated TS cells exclusively express Cx31 protein and Cx31.1 transcripts [2].
• We conclude that during trophoblast cell lineage differentiation, the Cx31 gap junction channel is involved in maintaining the proliferative diploid trophoblast cell population [2].
• Following implantation, Cx31 characterizes the early trophoblast cell lineage and is expressed by the spongiotrophoblast during placental development until birth [2].
• HeLa cells, which were stably transfected with wild type and the two different mutant Cx31-cDNA constructs, were analyzed for expression, phosphorylation, localization, formation of functional gap junction channels, and degradation of mutant Cx31 protein [3].

Biological context of Gjb3

• To study the function of this gene in mice, we generated animals with targeted replacement of the Cx31 gene (Gjb3) by a lacZ reporter gene [4].
• The connexin genes Cx31 and Cx45 coding for proteins of gap junctional subunits have been assigned to mouse chromosomes 4 and 11 by Southern blot hybridization of specific gene probes to DNA from mouse x Chinese hamster somatic cell hybrids [5].
• To characterize the role of Cx31 phosphorylation, serine residues 263 and 266 (Cx31Delta263,266) or 266 (Cx31Delta266) alone were exchanged for amino acids that cannot be phosphorylated [3].
• We conclude that Cx31 is essential for early placentation but can be compensated for by other connexins in the embryo proper and adult mouse [4].
• This study shows that Cx31/Cx43 double-deficient mice exhibit the known phenotypes of the single-knockout strains but no combined effects [6].

Anatomical context of Gjb3

• Expression profiles of the connexin genes, Gjb1 and Gjb3, in the developing mouse cochlea [7].
• In the developing otocyst epithelium, some restricted domains expressed Gjb3 and Gjb1 whilst high levels of both transcripts were present in the surrounding mesenchymal tissue [7].
• Gjb3 and Gjb1 expression was spatiotemporally modulated within the sensory hair cells and the various supporting cells that compose the developing organ of Corti [7].
• 5. Placentas of Gjb3(-/-) embryos at ED 9.5 were smaller than controls as a result of severely reduced labyrinth and spongiotrophoblast size [4].
• No morphological or functional defects of skin or inner ear were observed in surviving adult Gjb3(-/-) mice [4].

Other interactions of Gjb3

• In the adult cochlea Gjb1 transcripts disappeared while Gjb3 expression remained present in fibrocytes with specific expression patterns [7].
• Interestingly three of them (coding for Cx31, Cx31.1, and Cx30.3) are preferentially expressed in skin [5].
• Taken together with other results (published or submitted), our findings indicate that at least four connexins (Cx31, 31.1, 43 and 45) contribute to gap junctions in preimplantation development [8].
• 5. This corresponds to a time period in which another connexin isoform, Connexin43, is upregulated in spongiotrophoblast cells of Cx31-deficient and control placentas [4].
• In addition, from E10.5-E11.5, Cx31 was expressed by a column of cells in ventral r4, most likely representing contralateral vestibulo-acoustic efferent neurons, immediately anterior to a ventral column expressing Cx36 at the same stage [9].

Analytical, diagnostic and therapeutic context of Gjb3

• After Northern blot hybridization, we detected two Cx31 transcripts of 1.9 and 2.3 kb in total mouse RNA from skin, keratinocyte-derived cell lines, and in testis [10].

References