Clinical and histologic phenotyping of mice deficient in a key cellular mechanotransducer, TAZ

Abstract

Purpose : TAZ, a transcriptional coactivator, plays an important role in mechanotransduction. In vitro studies demonstrate a role of TAZ signaling in corneal keratocyte to myofibroblast transdifferentiation, particularly when corneal fibroblasts are cultured on stiff matrices and treated with TGF-b. Despite this, the in vivo role of TAZ in corneal stromal wound healing has not been assessed. Prior to investigating the role of TAZ in wound healing, a complete baseline phenotypic assessment was performed on TAZ deficient mice.

Methods : A breeding colony was established using 129S-TAZ heterozygous knockout (KO) mice. A small cohort of mutant (heterozygote KO, n=6; homozygous KO mice, n=2) and wildtype littermate (WT, n=6) mice underwent pre- and post-dilated ophthalmic examinations using slit lamp biomicroscopy and indirect ophthalmoscopy at post-natal month two. Homozygous KO mice underwent clinical examination only. Diagnostic assessment of heterozygous KO and WT mice included measurement of the palpebral length, phenol red threat test (PRTT), corneal sensitivity, and intraocular pressure (IOP). After clinical examination and diagnostics, mice were euthanized and tissues were formalin fixed for routine histopathologic assessment. Student’s t-tests were performed to test for differences between KO and WT mice.

Results : Breeding resulted in 86 offspring which were genotyped: 25 WT, 59 TAZ heterozygous KOs, and only 2 TAZ homozygous KOs. In the cohort of mice examined, all exhibited multifocal punctate nuclear cataractous changes. There were no anterior or posterior segment lesions identified with slit lamp biomicroscopy and indirect ophthalmoscopy. No significant differences were detected in palpebral length, PRTT, corneal sensitivity or IOP between the TAZ heterozygote KO and WT controls. Lastly, no histologic abnormalities were noted, both systemically and within the globes, in TAZ heterozygous KO mice.

Conclusions : The low number of TAZ homozygous KO mice suggest a failure in fertilization or embryonic death. No single gene knockout-specific anatomic abnormality was identified during the clinical and histologic phenotyping of TAZ deficient mice. Future efforts will expand the assessments of homozygous KO mice. These important findings will help to isolate the functional consequences of TAZ deficiency in the context of corneal wound healing in ongoing studies.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.