Investigating the possibility of Notch signalling in the adult retina
Date
2013-08-28
Authors
Ronellenfitch, Kara
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Abstract
The Notch signalling pathway is a highly conserved cell-to-cell signalling pathway
involved in developmental cell fate determination in all metazons. When Notch is
signalling, differentiation is inhibited and a progenitor-like state is favoured. This
signalling pathway has been implicated in the developing retina, where the inhibition of
Notch has been shown to skew the proportion of different retinal neuronal cell types.
Although functional knockout studies have allowed us to characterize some of the roles
of Notch in the retina, low protein levels have made it difficult to characterize the
location of Notch receptors and ligands in neuronal tissue. Here we sought to characterize
the localization of the Notch signalling pathway components in both the developing and
the adult mouse retina. Using RT-PCR we were able to show the presence of mRNA for
Notch receptors, ligands, and DNA binding cofactors for the Notch intracellular domain,
CBF1, throughout postnatal development as well as in the adult retina. In situ
hybridization confirmed the presence of Notch1, Notch2, and CBF1 mRNA in the
embryonic (E14.5) and early postnatal (P1.5) retina similar to what has been reported in
earlier studies, but in the adult retina (P40), levels were below detection. To further
explore the role of Notch in the adult retina we used two transgenic mouse reporter
models in which a Notch responsive element directs the expression of EGFP or Venus.
In the adult retina of the NTR line (Tg(Cp-EGFP)25Gaia/J) reporter expression was
detected in rod ON and cone type 2 OFF bipolar cells, as well as in a subset of both
amacrine and ganglion cells. In the CBFRE:H2B-Venus line adult reporter expression
was detected in photoreceptors, and a large proportion of both amacrine and ganglion
cells. Together this data supports the conclusion that Notch is expressed and actively
signalling in the retina throughout development and possibly in the adult retina, although below levels of in situ hybridization detection. These results represent the possibility of a
previously unknown role for Notch in the adult retina.
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Keywords
retina, notch