Expression and localization of gastrin messenger RNA and peptide in spermatogenic cells.

Abstract

In previous studies we have shown that the gene encoding cholecystokinin (CCK) is expressed in spermatogenic cells of several mammalian species. In the present study we show that a gene homologous to the CCK-related hormone, gastrin, is expressed in the human testis. The mRNA hybridizing to a human gastrin cDNA probe in the human testis was of the same size (0.7 kb) as gastrin mRNA in the human antrum. By in situ hybridization the gastrinlike mRNA was localized to seminiferous tubules. Immunocytochemical staining of human testis revealed gastrinlike peptides in the seminiferous tubules primarily at a position corresponding to spermatids and spermatozoa. In ejaculated spermatozoa gastrinlike immunoreactivity was localized to the acrosome. Acrosomal localization could also be shown in spermatids with electron microscopy. Extracts of the human testis contained significant amounts of progastrin, but no bioactive amidated gastrins. In contrast, ejaculated sperm contained mature carboxyamidated gastrin 34 and gastrin 17. The concentration of gastrin in ejaculated human spermatozoa varied considerably between individuals. We suggest that amidated gastrin (in humans) and CCK (in other mammals) are released during the acrosome reaction and that they may be important for fertilization. (J. Clin. Invest. 1990. 86:660-669.) Key words: activation * cholecystokinin. fertilization -neuropeptide -sperm Introduction The gastrointestinal hormones gastrin and cholecystokinin (CCK)' are homologous. They share an identical carboxyl-terminus Gly-Trp-Met-Asp-Phe-NH2, which contains the active site ofboth hormones (1, 2). The active site homology explains the overlapping spectra ofactivity and suggests that gastrin and CCK are derived from a common ancestor (3). This suggestion is supported by analysis of mammalian gastrin and CCK preprohormone structures (4-9) and by the recent detection of an invertebrate hybrid of mammalian gastrin and CCK (10).

In vivo analysis of mouse gastrin gene regulation in enhanced GFP-BAC transgenic mice

“…Gastrin has been reported to be expressed not only in the antrum but other organs such as the duodenum, pancreas, brain, pituitary glands, testis, and ovary in variety of species (11,12,27,29). In this study, we detected weak GFP signals in the anterior lobe of the pituitary gland, but not in the other organs such as duodenum, pancreas, testis, or ovary of the adult mouse.…”

“…Studies in the past that have relied primarily on radioimmunoassay of tissue extracts have reported gastrin expression in the organs other than stomach, such as pituitary gland, brain, testis, and ovary (11,12,27,29). Therefore, we investigated the possible presence of GFP expression in these tissues.…”

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

“…The gene encoding the neurotransmitter/neuromodulator cholecystokinin (CCK) has been shown to be expressed in male germ cells of several species, with an accumulation of the peptide in the acrosomal granule (8). In man, similar observations have been made for the CCK-related hormone gastrin (9). The results of these studies suggest that CCK peptides, and gastrin peptides in man, can be released during the acrosome reaction and therefore may be one of the components that activate the oocyte for fertilization.…”

Molecular structure and genetic mapping of the mouse gastrin gene

“…In adult vertebrates, the primary site of gastrin synthesis is the antral G-cells in the stomach. However, gastrin peptides have also been detected in the small and large intestine [2], vagal nerve [3], ovary [4], testis [5], hypothalamus and pituitary gland [6]. Moreover, during fetal life, gastrin is expressed in the pancreas [7], and colorectal tissues [8].…”