Lens-specific conditional knockout of tropomyosin 1 gene in mice causes abnormal fiber differentiation and lens opacity

Teppei Shibata; Masahito Ikawa; Ryo Sakasai; Yasuhito Ishigaki; Etsuko Kiyokawa; Kuniyoshi Iwabuchi; Dhirendra P Singh; Hiroshi Sasaki; Eri Kubo

doi:10.1016/j.mad.2021.111492

Lens-specific conditional knockout of tropomyosin 1 gene in mice causes abnormal fiber differentiation and lens opacity

Mech Ageing Dev. 2021 Jun:196:111492. doi: 10.1016/j.mad.2021.111492. Epub 2021 Apr 15.

Authors

Teppei Shibata¹, Masahito Ikawa², Ryo Sakasai³, Yasuhito Ishigaki⁴, Etsuko Kiyokawa⁵, Kuniyoshi Iwabuchi³, Dhirendra P Singh⁶, Hiroshi Sasaki¹, Eri Kubo⁷

Affiliations

¹ Department of Ophthalmology, Kanazawa Medical University, Ishikawa, Japan.
² Research Institute for Microbial Diseases, Osaka University, Osaka, Japan.
³ Department of Biochemistry I, Kanazawa Medical University, Ishikawa, Japan.
⁴ Medical Research Institute, Kanazawa Medical University, Ishikawa, Japan.
⁵ Department of Oncologic Pathology, Kanazawa Medical University, Ishikawa, Japan.
⁶ Department of Ophthalmology and Visual Sciences, University of Nebraska Medical Center, Omaha, NE, USA.
⁷ Department of Ophthalmology, Kanazawa Medical University, Ishikawa, Japan. Electronic address: kuboe@kanazawa-med.ac.jp.

PMID: 33862037
DOI: 10.1016/j.mad.2021.111492

Abstract

Tropomyosin (Tpm) 1 and 2 are important in the epithelial mesenchymal transition of lens epithelial cells; however, the effect of Tpm1 depletion during aging remains obscure. We analyzed the age-related changes in the crystalline lens of Tpm1- conditional knockout mice (Tpm1-CKO). Floxed alleles of Tpm1 were conditionally deleted in the lens, using Pax6-cre transgenic mice. Lenses of embryonic day (ED) 14, postnatal 1-, 11-, and 48-week-old Tpm1-CKO and wild type mice were dissected to prepare paraffin sections, which subsequently underwent histological and immunohistochemical analysis. Tpm1 and α smooth muscle actin (αSMA) mRNA expression were assessed using RT-PCR. The homozygous Tpm1-CKO (Tpm1^-/-) lenses displayed a dramatic reduction in Tpm1 transcript, with no change to αSMA mRNA expression. Tpm1^-/- mice had small lenses with disorganized, vesiculated fiber cells, and loss of epithelial cells. The lenses of Tpm1^-/- mice had abnormal and disordered lens fiber cells with cortical and peri-nuclear liquefaction. Expression of filamentous-actin was reduced in the equator region of lenses derived from ED14, 1-, 11-, and 48-week-old Tpm1^-/- mice. Therefore, Tpm1 plays an integral role in mediating the integrity and fate of lens fiber differentiation and lens homeostasis during aging. Age-related Tpm1 dysregulation or deficiency may induce cataract formation.

Keywords: Lens; Lens fiber differentiation; Lens opacity; Tropomyosin.

Publication types

Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't

MeSH terms

Actins / metabolism*
Aging / physiology*
Animals
Cataract* / metabolism
Cataract* / pathology
Cataract* / physiopathology
Cell Differentiation
Cellular Senescence / physiology*
Epithelial-Mesenchymal Transition / physiology
Gene Expression Profiling
Immunohistochemistry
Lens, Crystalline / metabolism
Lens, Crystalline / pathology
Mice
Mice, Knockout
RNA, Messenger
Tropomyosin / genetics*

Substances

Acta2 protein, mouse
Actins
RNA, Messenger
Tpm1 protein, mouse
Tropomyosin

Grants and funding

R01 EY024589/EY/NEI NIH HHS/United States