Limits...
The molecular basis of defective lens development in the Iberian mole.

Carmona FD, Jiménez R, Collinson JM - BMC Biol. (2008)

Bottom Line: Fossorial mammals face natural selection pressures that differ from those acting on surface dwelling animals, and these may lead to reduced visual system development.PAX6 is not down-regulated in developing lens fibre nuclei, as it is in other species, and there is ectopic expression of FOXE3, a putative downstream effector of PAX6, in some, but not all lens fibres.The undifferentiated status of the anterior epithelial cells was compromised, and most of them undergo apoptosis.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK. d.carmona@abdn.ac.uk

ABSTRACT

Background: Fossorial mammals face natural selection pressures that differ from those acting on surface dwelling animals, and these may lead to reduced visual system development. We have studied eye development in a species of true mole, the Iberian mole Talpa occidentalis, and present the molecular basis of abnormal lens development. This is the first embryological developmental study of the eyes of any fossorial mammal at the molecular level.

Results: Lens fibre differentiation is not completed in the Iberian mole. Although eye development starts normally (similar to other model species), defects are seen after closure of the lens vesicle. PAX6 is not down-regulated in developing lens fibre nuclei, as it is in other species, and there is ectopic expression of FOXE3, a putative downstream effector of PAX6, in some, but not all lens fibres. FOXE3-positive lens fibres continue to proliferate within the posterior compartment of the embryonic lens, but unlike in the mouse, no proliferation was detected anywhere in the postnatal mole lens. The undifferentiated status of the anterior epithelial cells was compromised, and most of them undergo apoptosis. Furthermore, beta-crystallin and PROX1 expression patterns are abnormal and our data suggest that genes encoding beta-crystallins are not directly regulated by PAX6, c-MAF and PROX1 in the Iberian mole, as they are in other model vertebrates.

Conclusion: In other model vertebrates, genetic pathways controlling lens development robustly compartmentalise the lens into a simple, undifferentiated, proliferative anterior epithelium, and quiescent, anuclear, terminally differentiated posterior lens fibres. These pathways are not as robust in the mole, and lead to loss of the anterior epithelial phenotype and only partial differentiation of the lens fibres, which continue to express 'epithelial' genes. Paradigms of genetic regulatory networks developed in other vertebrates appear not to hold true for the Iberian mole.

Show MeSH

Related in: MedlinePlus

Lens fibre cells proliferation in the Iberian mole. (A) 3,3'-Diaminobenzidine tetrahydrochloride-immunostaining for PH3 on both mouse and mole wax sections at different embryonic stages. During mouse lens differentiation, proliferating cells (immunoreactive for PH3) are always found in the anterior epithelium (E12, E15). In the mole, very few PH3-positive cells were detected between the s4c and s5c stages, and most of them were located in the posterior region of the lens (arrows). No proliferation was observed in the lens at s7 and subsequent stages. (B) Double-immunofluorescence for PH3 (red) and FOXE3 (green) on wax sections of s5b and s5c mole samples. All the PH3-positive cells showed immunoreactivity against the anti-FOXE3 antibody. The nuclei are stained blue with 4'6-diamidino-2-phenylindole stain. Photomicrographs were taken using a single bandpass fluorescence mirror unit and merged with 'The Gimp' software. Black scale bar represents 200 μm in all figures of A, and white scale bar represents 50 μm in all figures of B.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2587461&req=5

Figure 8: Lens fibre cells proliferation in the Iberian mole. (A) 3,3'-Diaminobenzidine tetrahydrochloride-immunostaining for PH3 on both mouse and mole wax sections at different embryonic stages. During mouse lens differentiation, proliferating cells (immunoreactive for PH3) are always found in the anterior epithelium (E12, E15). In the mole, very few PH3-positive cells were detected between the s4c and s5c stages, and most of them were located in the posterior region of the lens (arrows). No proliferation was observed in the lens at s7 and subsequent stages. (B) Double-immunofluorescence for PH3 (red) and FOXE3 (green) on wax sections of s5b and s5c mole samples. All the PH3-positive cells showed immunoreactivity against the anti-FOXE3 antibody. The nuclei are stained blue with 4'6-diamidino-2-phenylindole stain. Photomicrographs were taken using a single bandpass fluorescence mirror unit and merged with 'The Gimp' software. Black scale bar represents 200 μm in all figures of A, and white scale bar represents 50 μm in all figures of B.

Mentions: Cell proliferation was studied by analysing the presence of the phosphorylated form of the histone H3 (PH3). In wild-type mouse samples, this protein was observed in some cells throughout the lens vesicle at E12 (Figure 8A), but was restricted to the lens epithelium by E15, as described previously [18]. In the mole, PH3-positive cells were scarce in comparison to equivalent stages in mice. From stage s4c on, only one or two mitotic lens cells were seen per section, with most sections showing no proliferating cells. PH3 was frequently detected in the elongating cells located at the posterior side of the lens between stages s5a and s6. No proliferating cells were observed at s7 and later stages of the mole lens development (N ≥ 4 lenses/stage), whereas PH3 labelling was observed in all mouse lens epithelia at all stages. Hence patterns of proliferation are spatially deregulated in the mole lens, and proliferation is prematurely terminated with lens growth after s7 presumably relying solely on the increasing size of lens fibres.


The molecular basis of defective lens development in the Iberian mole.

Carmona FD, Jiménez R, Collinson JM - BMC Biol. (2008)

Lens fibre cells proliferation in the Iberian mole. (A) 3,3'-Diaminobenzidine tetrahydrochloride-immunostaining for PH3 on both mouse and mole wax sections at different embryonic stages. During mouse lens differentiation, proliferating cells (immunoreactive for PH3) are always found in the anterior epithelium (E12, E15). In the mole, very few PH3-positive cells were detected between the s4c and s5c stages, and most of them were located in the posterior region of the lens (arrows). No proliferation was observed in the lens at s7 and subsequent stages. (B) Double-immunofluorescence for PH3 (red) and FOXE3 (green) on wax sections of s5b and s5c mole samples. All the PH3-positive cells showed immunoreactivity against the anti-FOXE3 antibody. The nuclei are stained blue with 4'6-diamidino-2-phenylindole stain. Photomicrographs were taken using a single bandpass fluorescence mirror unit and merged with 'The Gimp' software. Black scale bar represents 200 μm in all figures of A, and white scale bar represents 50 μm in all figures of B.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2587461&req=5

Figure 8: Lens fibre cells proliferation in the Iberian mole. (A) 3,3'-Diaminobenzidine tetrahydrochloride-immunostaining for PH3 on both mouse and mole wax sections at different embryonic stages. During mouse lens differentiation, proliferating cells (immunoreactive for PH3) are always found in the anterior epithelium (E12, E15). In the mole, very few PH3-positive cells were detected between the s4c and s5c stages, and most of them were located in the posterior region of the lens (arrows). No proliferation was observed in the lens at s7 and subsequent stages. (B) Double-immunofluorescence for PH3 (red) and FOXE3 (green) on wax sections of s5b and s5c mole samples. All the PH3-positive cells showed immunoreactivity against the anti-FOXE3 antibody. The nuclei are stained blue with 4'6-diamidino-2-phenylindole stain. Photomicrographs were taken using a single bandpass fluorescence mirror unit and merged with 'The Gimp' software. Black scale bar represents 200 μm in all figures of A, and white scale bar represents 50 μm in all figures of B.
Mentions: Cell proliferation was studied by analysing the presence of the phosphorylated form of the histone H3 (PH3). In wild-type mouse samples, this protein was observed in some cells throughout the lens vesicle at E12 (Figure 8A), but was restricted to the lens epithelium by E15, as described previously [18]. In the mole, PH3-positive cells were scarce in comparison to equivalent stages in mice. From stage s4c on, only one or two mitotic lens cells were seen per section, with most sections showing no proliferating cells. PH3 was frequently detected in the elongating cells located at the posterior side of the lens between stages s5a and s6. No proliferating cells were observed at s7 and later stages of the mole lens development (N ≥ 4 lenses/stage), whereas PH3 labelling was observed in all mouse lens epithelia at all stages. Hence patterns of proliferation are spatially deregulated in the mole lens, and proliferation is prematurely terminated with lens growth after s7 presumably relying solely on the increasing size of lens fibres.

Bottom Line: Fossorial mammals face natural selection pressures that differ from those acting on surface dwelling animals, and these may lead to reduced visual system development.PAX6 is not down-regulated in developing lens fibre nuclei, as it is in other species, and there is ectopic expression of FOXE3, a putative downstream effector of PAX6, in some, but not all lens fibres.The undifferentiated status of the anterior epithelial cells was compromised, and most of them undergo apoptosis.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK. d.carmona@abdn.ac.uk

ABSTRACT

Background: Fossorial mammals face natural selection pressures that differ from those acting on surface dwelling animals, and these may lead to reduced visual system development. We have studied eye development in a species of true mole, the Iberian mole Talpa occidentalis, and present the molecular basis of abnormal lens development. This is the first embryological developmental study of the eyes of any fossorial mammal at the molecular level.

Results: Lens fibre differentiation is not completed in the Iberian mole. Although eye development starts normally (similar to other model species), defects are seen after closure of the lens vesicle. PAX6 is not down-regulated in developing lens fibre nuclei, as it is in other species, and there is ectopic expression of FOXE3, a putative downstream effector of PAX6, in some, but not all lens fibres. FOXE3-positive lens fibres continue to proliferate within the posterior compartment of the embryonic lens, but unlike in the mouse, no proliferation was detected anywhere in the postnatal mole lens. The undifferentiated status of the anterior epithelial cells was compromised, and most of them undergo apoptosis. Furthermore, beta-crystallin and PROX1 expression patterns are abnormal and our data suggest that genes encoding beta-crystallins are not directly regulated by PAX6, c-MAF and PROX1 in the Iberian mole, as they are in other model vertebrates.

Conclusion: In other model vertebrates, genetic pathways controlling lens development robustly compartmentalise the lens into a simple, undifferentiated, proliferative anterior epithelium, and quiescent, anuclear, terminally differentiated posterior lens fibres. These pathways are not as robust in the mole, and lead to loss of the anterior epithelial phenotype and only partial differentiation of the lens fibres, which continue to express 'epithelial' genes. Paradigms of genetic regulatory networks developed in other vertebrates appear not to hold true for the Iberian mole.

Show MeSH
Related in: MedlinePlus