Date of Award
Doctor of Philosophy
Gap junctions provide for the transfer of low molecular weight molecules and ions between cytoplasms of adjacent cells. Connexins exist as a multigene family with one or more members found in almost all adult tissues. In the central nervous system, gap junctions have been detected in a variety of cell types including neurons, astrocytes and oligodendrocytes. Gap junctions have been detected in the developing brain in a spacial and temporal pattern. This study examines gap junction expression and cellular specificity during development of the rodent central nervous system. To investigate the role of gap junctions during development, a model of neural development is examined with respect to its connexin expression.;In the developing rodent brain, connexin32 and connexin43 were detected by Northern blot analysis. Connexin43 mRNA was detected pre- and postnatally, whereas connexin32 mRNA was differentially expressed, being first detectable at postnatal day 10 in hindbrain and day 15 in forebrain. Western blot analysis demonstrated the presence of connexin protein during postnatal development of the rodent brain. To examine connexin expression in greater detail, in situ hybridization studies were performed. Connexin43 mRNA was found in the leptomeninges and astrocytes. Oligodendrocytes and select populations of neurons were shown to express connexin32 mRNA. Cultured astrocytes express cx43 confirming the in vivo findings. Initially, in culture, neurons express connexin26 protein which becomes less abundant with time. Neurons cultured for extended periods of time express cx32.;The embryonal carcinoma cell line, P19, differentiates into neurons and astrocytes following treatment with retinoic acid. Undifferentiated P19 cells express connexin26 and 43. The mRNA level of these two connexins do not change when P19 cells were exposed to retinoic acid. Connexin43 protein, however, is significantly reduced after exposure to retinoic acid. During differentiation, the neurons expressed connexin26 and astroctyes expressed connexin43.;These investigations have determined that gap junctions are differentially expressed during development of the central nervous system. Astrocytes express connexin43 whereas neurons and oligodendrocytes express connexin32. Connexin26 is present in immature neurons in culture. The studies on P19 cells further support the presence of connexin26 in neurons and represents a model of neural differentiation that modulates connexin expression.
Belliveau, Daniel J., "Gap Junction Gene Expression In The Developing Nervous System" (1994). Digitized Theses. 2342.