Localization of laminin B1 mRNA in retinal ganglion cells by in situ hybridization.

Abstract

Abstract. In the nervous system, neuronal migration and axonal growth are dependent on specific interactions with extracellular matrix proteins. During development of the vertebrate retina, ganglion cell axons extend along the internal limiting (basement) membrane and form the optic nerve. Laminin, a major component of basement membranes, is known to be present in the internal limiting membrane, and might be involved in the growth of ganglion cell axons. The identity of the cells that produce retinal laminin, however, has not been established. In the present study, we have used in situ hybridization to localize the sites of laminin B1 mRNA synthesis in the developing mouse retina. Our results show that there are at least two principal sites of laminin B1 mRNA synthesis: (a) the hyaloid vessels and the lens during the period of major axonal outgrowth, and (b) the retinal ganglion cells at later development stages. Mtiller (glial) cells, the major class of nonneuronal cells in the retina, do not appear to express laminin B1 mRNA either during development or in the adult retina. In Northern blots, we found a single transcript of ~6-kb size that encodes the laminin B1 chain in the retina. Moreover, laminin B1 mRNA level was four-to fivefold higher in the postnatal retina compared to that in the adult. Our results show that in addition to nonneuronal cells, retinal ganglion cells also synthesize laminin. The function of laminin in postnatal retinas, however, remains to be elucidated. Nevertheless, our findings raise the possibility that neurons in other parts of the nervous system might also synthesize extracellular matrix proteins.

Distribution of the ten known laminin chains in the pathways and targets of developing sensory axons

“…9A,B,D-F,H). Laminin chains have been reported to be expressed in retina during development (Sarthy and Fu, 1990;Morissette and Carbonetto, 1995). In support of these findings, we observed laminin a2, a4, and g1 expression in retina (arrowheads in Fig.…”

“…Perhaps surprisingly, we find that laminin chains are either not expressed or expressed diffusely at low levels in the gray matter of the spinal cord. Our results obviously do not preclude laminin expression in other regions of the CNS at some stage of development (e.g., see Sarthy and Fu, 1990;Morissette and Carbonetto, 1995).…”

Laminin‐1 increases motility, path‐searching, and process dynamism of rat and mouse Muller glial cells in vitro: Implication of relationship between cell behavior and formation of retinal morphology

“…Neither embryonic nor adult mouse Muller cells express the ␤1 subunit of the laminin-1 heterotrimer. However, ganglion cells located at Muller glial endfeet were proved to express the ␤1 subunit [Sarthy and Fu, 1990]. This phenomenon may be of developmental significance as Muller cell processes arrive and form endfeet at the vitread border of the retina when ganglion cells have already been located there [Reichenbach and Robinson, 1995].…”

Proteins in unexpected locations.

“…Laminin is expressed as a mixture of diffuse and punctate staining patterns within different subsets of neuronal perikarya in the mature, but not in the developing, brain (Yamamato et al, 1988;Hagg et al, 1989;Zhou, 1990;Jucker et al, 1992). Neurons appear to synthesize laminin because an in situ hybridization study has confirmed that retinal ganglion cells synthesize laminin Bi chain mRNA (Sarthy and Fu, 1990) and because immunoelectron microscopy has demonstrated the presence of laminin associated with rough ER and lysosomes (Yamamoto et al, 1988 (cf. Huang et al, 1995).…”