Department of Life Science and Institute for Natural Sciences, Hanyang University, Seoul, South Korea.
Andrologia. 2012 May;44 Suppl 1:383-9. doi: 10.1111/j.1439-0272.2011.01195.x. Epub 2011 Oct 6.
Vitamin B(12) (cobalamin) deficiency results in atrophy of seminiferous tubules and aplasia of spermatozoa and spermatid. The transmembrane protein amnionless (AMN) directs endocytosis of cubilin with its ligand, contributing to intrinsic factor-vitamin B(12) absorption. To understand vitamin B(12) transport in testis, we analysed AMN expression in developing mouse testes and in Leydig cells and speculated the possible role of AMN in testis. In testes, Amn mRNA levels were low until 14 days post partum (pp) and markedly increased from puberty onwards. In the interstitium, Amn mRNA levels were low at 14 days pp and increased at puberty (28 days pp) together with 3-beta-hydroxysteroid dehydrogenase type 6 mRNA. Strong AMN immunoreactivity was observed in early spermatocytes from 7 days pp, suggesting that AMN participates in meiosis. In Leydig cells, AMN was not observed until 14 days pp but was strongly expressed after 28 days pp, suggesting a positive relationship between AMN expression and functional differentiation of adult Leydig cells. Together, AMN may participate in meiosis in early spermatocytes and in functional differentiation of adult Leydig cells through the mediation of vitamin B(12) transport in the mouse testes. This is the first report on AMN expression in the germ cells and soma of mammalian testes.
维生素 B(12)（钴胺素）缺乏会导致生精小管萎缩和精子及精原细胞发育不良。跨膜蛋白 Amnionless（AMN）指导其配体内吞作用，从而促进内在因子-维生素 B(12)吸收。为了了解睾丸中的维生素 B(12)转运，我们分析了 AMN 在发育中的小鼠睾丸和 Leydig 细胞中的表达，并推测了 AMN 在睾丸中的可能作用。在睾丸中，Amn mRNA 水平在出生后 14 天（pp）之前较低，并从青春期开始显著增加。在间质中，Amn mRNA 水平在 14 天 pp 时较低，并在青春期（28 天 pp）与 3-β-羟类固醇脱氢酶类型 6 mRNA 一起增加。从 7 天 pp 的早期精母细胞中观察到强烈的 AMN 免疫反应，表明 AMN 参与减数分裂。在 Leydig 细胞中，直到 14 天 pp 才观察到 AMN，但在 28 天 pp 后强烈表达，表明 AMN 表达与成年 Leydig 细胞的功能分化之间存在正相关。总之，AMN 可能通过介导小鼠睾丸中的维生素 B(12)转运，参与早期精母细胞的减数分裂和成年 Leydig 细胞的功能分化。这是 AMN 在哺乳动物睾丸生殖细胞和体细胞中表达的首次报道。
