Expression of choline acetyltransferase mRNA in spermatogenic cells results in an accumulation of the enzyme in the postacrosomal region of mature spermatozoa.

Abstract

The gene encoding choline acetyltransferase (ChAT; EC 2.3.1.6), the key enzyme in the synthesis of the neurotransmitter acetylcholine (ACh), is shown to be expressed in rat and human testes. High levels of two ChAT transcripts of 3.5 and 1.3 kilobases were detected by Northern blot analysis of adult rat testis RNA. A single ChAT mRNA species of 3.2 kilobases was detected in human testis. Cells responsible for the synthesis of ChAT mRNA in rat testis were localized by in situ hybridization in the middle part ofthe seminiferous epithelium, where the labeling was mostly found over spermatocytes and spermatids. Studies on the ontogeny of ChAT mRNA expression showed low levels in prepubertal rats with increasing levels as sexual maturation is reached. A peak of expression was seen at postnatal day 32, correlating with the onset of postmeiotic spermatogenesis. Results from surgical and pharmacological treatments suggest that androgens, as well as pituitary factors, could influence the relative levels of the two ChAT mRNAs detected in rat testis. Evidence for translation of the mRNA detected in the testis was obtained from the demonstration of ChAT-like immunoreactivity in ejaculated human spermatozoa. The staining was restricted to the postacrosomal region of the head, where the membrane ofthe sperm first fuses with that of the egg during fertilization, and to the annulus, a ring of dense material in the caudal end of the midpiece. Combined, these findings support the hypothesis that the neurotransmitter ACh is involved in reproductive function.

Regulatory region in choline acetyltransferase gene directs developmental and tissue-specific expression in transgenic mice.

“…2C, and data not shown). Interestingly, none of the 8 lines expressed the transgene in the testis, where germ cells have been shown to express ChAT mRNA at high levels (33).…”

Immunohistochemical evidence suggests intrinsic regulatory activity of human eccrine sweat glands

“…Our results indicate that acetylcholine could be synthesised in myoepithelial cells. This is not entirely surprising because ChAT has been found in nonneuronal human tissues, namely ejaculated spermatozoa (Ibanez et al 1991), myoblasts and myotubes (Hamann et al 1995) and the chorion (Oda et al 1996). Myoepithelial cells subserve the rapid excretion of sweat on stimulation and\or ' provide mechanical support for the secretory coil wall against the increase in luminal hydrostatic pressure ' (Sato et al 1989), and the ChAT activity therein could contribute to regulation of contractile activity.…”

Cloning of the rat gene encoding choline acetyltransferase, a cholinergic neuron-specific marker.

“…Northern blot analyses identified four different ChAT mRNAs in rat brain (11,16), spinal cord (9, 11), testis (16), and PC12 cells (Fig. 1B), suggesting that different modes of RNA synthesis, such as alternative splicing or differential transcription initiation, are operative in these tissues.…”

“…In contrast, a shorter message (=2.9 kb) was detected in PC12 cells. Recently, IbAfiez et al (16) identified two ChAT messages (3.5 kb and 1.3 kb) in the rat testis, which differed in size from the neuronal form. When the RNAs from rat testis, spinal cord, and PC12 cells were electrophoresed in parallel, the ChAT messages in these samples all migrated with different mobilities (data not shown).…”