Molecular cloning and expression profile of rat myocilin

Myocilin is known to be associated with the pathogenesis of juvenile-onset primary open angle glaucoma, The tissue distribution of myocilin transcript s has been analyzed in both humans and mice, and a high level of expression in the retina and skeletal muscle has been reported. The functions of myoc ilin in these tissues are unknown. We isolated rat myocilin cDNA and examin ed the expression pattern. of myocilin, including its expression in endocri ne organs, using Northern blot analysis. The rat myocilin cDNA sequence has two in-frame initiation codons, the upstream and downstream ATGs correspon ding to the initiation. codon of human and murine myocilin, respectively. I t is most likely that the first ATG; is a translational initiation codon, s ince 8 of 13 amino acid residues deduced from the rat cDNA sequence between the first and the second ATGs are the same as those in human myocilin. The open reading frame encodes 502 amino acids. Rat myocilin also has both a m yosin-like domain and an olfactmedin-like domain, which have been identifie d in human and murine myocilin, Northern analysis of rat myocilin mRNA reve aled substantial expression in the thyroid gland, as well as in the retina and muscle. No transcripts were detected in other endocrine glands, includi ng the adrenal gland, pituitary, and testis, Myocilin may play an important role in thyroid function. Further study of the expression and role of myoc ilin in the thyroid is required. (C) 2000 Academic Press.