Abstract
Abstract: :
Purpose: Wnt signaling has been implicated in many cellular processes during development. Current research indicates that members of this growth factor family are involved in regulating differentiation and maintenance of the lens epithelium. This study investigated the mRNA expression patterns of Wnt receptors, the Frizzleds (Fzs), and the Wnt signaling antagonists, secreted frizzled-related proteins (sFRPs), during mouse lens morphogenesis. Methods: RNA, isolated from postnatal mouse lens epithelial cells, was reverse transcribed (RT) to cDNA and amplified by PCR using specific primers for Fzs and sFRPs. DIG-labelled riboprobes were prepared for each PCR fragment and in situ hybridisation (ISH) carried out. Paraffin sections of mice from embryonic day 10.5 (E10.5) to E18.5 and mouse eyes at postnatal day 7 (P7) and P21 were analysed for Fz and sFRP expression using an anti-DIG-AP conjugate. Results: RT-PCR for Fzs and sFRPs showed amplification of products at expected sizes for Fzs 1, 2, 3, 4 and 6 and sFRPs 1, 2 and 3. The identities of the Fzs and sFRPs were confirmed by cloning and sequencing. ISH showed that at embryonic day 10.5 (E10.5), Fzs and sFRPs were ubiquitously expressed in the lens pit. At stage E12.5, Fzs and sFRPs were expressed in the developing epithelium and primary fibres. At E14.5 Fzs continued to be expressed in the developing epthelium but were reduced in the primary fibres. At later embryonic stages Fzs were localised to the epithelium and equatorial region, including the transitional zone. During post-natal development expression continued to be detected in the anterior epithelium and equatorial region. sFRP1 had a similar pattern of expression to the Fzs during embryonic and postnatal development. However, sFRP2 was only detected in the developing epithelium particularly in the region above the lens equator. From E18.5, sFRP2 expression was not detected in any region of the lens.Conclusions: Multiple Fz receptors and sFRP antagonists are expressed during mouse lens development. Fzs have similar patterns of expression indicating a potential for some redundancy in the Wnt signalling system. However, sFRPs, show some differences in their patterns of expression. sFRPs can modulate the range and/or strength of active Wnt signalling and may have important roles in defining proliferation and differentiation compartments in the lens.
Keywords: growth factors/growth factor receptors • in situ hybridization • molecular biology