Atrx deficiency induces telomere dysfunction, endocrine defects, and reduced life span
L. Ashley Watson, Lauren A. Solomon, Jennifer Ruizhe Li, Yan Jiang, Matthew Edwards, Kazuo Shin-ya, Frank Beier, Nathalie G. Bérubé
L. Ashley Watson, Lauren A. Solomon, Jennifer Ruizhe Li, Yan Jiang, Matthew Edwards, Kazuo Shin-ya, Frank Beier, Nathalie G. Bérubé
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Research Article Aging

Atrx deficiency induces telomere dysfunction, endocrine defects, and reduced life span

Abstract

Human ATRX mutations are associated with cognitive deficits, developmental abnormalities, and cancer. We show that the Atrx-null embryonic mouse brain accumulates replicative damage at telomeres and pericentromeric heterochromatin, which is exacerbated by loss of p53 and linked to ATM activation. ATRX-deficient neuroprogenitors exhibited higher incidence of telomere fusions and increased sensitivity to replication stress–inducing drugs. Treatment of Atrx-null neuroprogenitors with the G-quadruplex (G4) ligand telomestatin increased DNA damage, indicating that ATRX likely aids in the replication of telomeric G4-DNA structures. Unexpectedly, mutant mice displayed reduced growth, shortened life span, lordokyphosis, cataracts, heart enlargement, and hypoglycemia, as well as reduction of mineral bone density, trabecular bone content, and subcutaneous fat. We show that a subset of these defects can be attributed to loss of ATRX in the embryonic anterior pituitary that resulted in low circulating levels of thyroxine and IGF-1. Our findings suggest that loss of ATRX increases DNA damage locally in the forebrain and anterior pituitary and causes tissue attrition and other systemic defects similar to those seen in aging.

Authors

L. Ashley Watson, Lauren A. Solomon, Jennifer Ruizhe Li, Yan Jiang, Matthew Edwards, Kazuo Shin-ya, Frank Beier, Nathalie G. Bérubé

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Figure 7

Loss of ATRX in the developing anterior pituitary causes DNA damage, reduced Tsh expression, and altered thyroid function.

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Loss of ATRX in the developing anterior pituitary causes DNA damage, red...
(A) Quantitative RT-PCR analysis of P23 control and cKO shows loss of Atrx expression in the pituitary (5.9-fold decrease) and thyroid (1.25-fold decrease). Tsha and Tshb subunits showed decreased expression in the pituitary, and a number of downstream targets of TSH showed decreased expression in the thyroid of cKO mice compared with controls (n = 3). (B) H&E staining of P23 control and cKO pituitary. Scale bar: 500 μm. (C) Immunofluorescence detection of ATRX expression in P23 control and cKO pituitary demonstrates specific loss of ATRX in the anterior and intermediate pituitary. Scale bars: 500 μm (left panels) and 50 μm (right panels). A, anterior; I, intermediate; P, posterior pituitary. (D) Immunofluorescence detection of ATRX in E13.5 control and cKO sagittal embryonic pituitary cryosections shows loss of ATRX expression. Scale bar: 100 μm. Pit, pituitary. (E) Immunofluorescence detection of γH2AX in E13.5 sagittal embryonic pituitary cryosections shows increased DNA damage in cKO embryonic pituitary compared with control. Scale bar: 100 μm. Original magnification, ×25 (C, left panels); ×100 (C, right panels, and E); ×50 (D). *P < 0.05.