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[Histological studies in the developing eyelids of congenital microphthalmic (Cts) mice]
1Department of Ophthalmology, Nagoya City University Medical School, Aichi-ken, Japan.
Abstract:
The Cts mouse is a mutant of the Jcl:ICR strain with congenital cataract and small eyes in homozygotes. In the present study, attempts were made to measure postnatally the palpebral fissure and to examine the process of eyelid development by light microscopy in both normal (+/+) and homozygous (Cts/Cts) mice. The width of the palpebral fissure in homozygotes was significantly smaller than in unaffected mice. To investigate the process of eyelid development, tissue specimens from normal and Cts homozygous mice were prepared with hematoxylin and eosin, and observed by light microscopy on days 14, 16, and 18 of gestation and on days 0, 7, and 14 after birth. In both groups, the eyelid fused on day 16 of gestation and opened completely on day 14 after birth. The primordium of the orbicularis oculi muscle was defined on day 16 of gestation, and the primordia of hair follicles and Meibomian glands were detected on day 18 of gestation. In the present study, there were no significant differences in the process of eyelid development between normal and homozygous mice. Eyelid development has thus far been thought to be self-determining and not affected by tissue interaction, and the present findings support this line of thought.
Insights
Congenital cataract (Cts) mice exhibit smaller palpebral fissures, but their eyelid development process is normal. This suggests eyelid development is self-determining, unaffected by the Cts mutation.
Area of Science:
- Developmental biology
- Ophthalmology
- Genetics
Context:
- The Cts mouse model displays congenital cataracts and microphthalmia (small eyes).
- Previous understanding suggests eyelid development is an autonomous process.
- Investigating the Cts mutation's impact on eyelid development is crucial for understanding ocular abnormalities.
Purpose:
- To quantitatively assess palpebral fissure width in Cts homozygous mice postnatally.
- To histologically examine eyelid development stages in normal and Cts homozygous mice.
- To determine if the Cts mutation affects the timing or process of eyelid fusion and opening.
Summary:
- Palpebral fissure width was significantly reduced in Cts/Cts mice compared to wild-type (+/+).
- Light microscopy revealed no significant differences in eyelid fusion, opening, or the development of associated structures (orbicularis oculi muscle, hair follicles, Meibomian glands) between genotypes.
- Eyelid development proceeded normally in Cts homozygous mice, with fusion on gestation day 16 and complete opening by postnatal day 14.
Impact:
- These findings support the hypothesis that eyelid development is a self-determining process.
- The study indicates that the genetic factors causing congenital cataracts and microphthalmia in Cts mice do not directly interfere with normal eyelid morphogenesis.
- Provides a basis for further research into the specific genetic mechanisms of congenital cataract and microphthalmia independent of eyelid development.