Structures related to the germ plasm in mouse

SummaryThis report presents data from ultrastructural and morphometric studies on the germinal-body-like structures, nuage, nuage–mitochondrial clusters and chromatoid bodies in 4.5-day embryo cells and spermatogenic cells of the laboratory mouse Mus musculus. In the 4.5-day embryo cells the germinal-body-like structures that, according to previous data, arise by condensation of mitochondria in Graafian oocytes, were found not to undergo any ultrastructural alterations. In spermatogonia the germinal-body-like structures presumably were transformed into nuage that functioned as ‘intermitochondrial cement’ binding the mitochondrial clusters. In primary spermatocytes mitochondria aggregated by nuage were found with large vacuoles containing membraneous conglomerates that were obviously excreted by organelles into the cytoplasm. The chromatoid bodies that arose in spermatocytes and finally disintegrated in the posterior part of late spermatids seemed not to be implicated in the pathway of the germinal-body-like structure. The dispersion of chromatoid bodies was noted to be accompanied by excretion of membraneous conglomerates by late spermatid mitochondria. The spermatozoa were not found to contain either the germinal-body-like structures or any other germ-plasm-related structures.

263 IDENTIFICATION OF A NOVEL MOPT GENE IN HUMAN AND MOUSE ADULT TESTIS

To discover late stage germ cell-specific transcripts we prepared a cDNA library from adult testes of 35-day old mice and subtracted it with mRNA from the testes of juvenile mice. Real-time RT-PCR analysis indicated that 42 cDNA clones in the subtracted library were expressed more intensely in the adult testes than in the juvenile testes. One clone identified by subtraction is expressed preferentially in the late spermatid and is located on chromosome 17E3 in mouse and 2p22 in human. The full nucleotide and amino acid sequences of mouse and human MOPT gene are deposited in EMBL GenBank (AY367765 And AY367766). Human MOPT is spliced by 5 exons and 4 introns and encompasses 7,000 bp of genomic DNA (from bp 355 822 to 425 511) of NT-022184.13, whereas mouse MOPT is spliced by 5 exons and 4 introns and encompasses 7,382 bp of genomic DNA (from bp 6227407 to 6235588) of NT-039658.2. Because of the limited availability of human testis samples, development-dependent expression of MOPT mRNA was conducted using its mouse homologue and semiquantitative PCR. The number of cycles completed before entering the exponential growth, recorded by amplifier PE5700 for mouse MOPT, were 1.11 ± 0.23, 1.05 ± 0.04, 1.5 ± 0.2, 5.55 ± 0.65, 19.35 ± 0.65, 68.65 ± 2.15, and 185.15 ± 6.15 in W/W, postnatal day 5-, 8-, 12-, 15-, 18-, 22-, and 28-day mouse tissue samples, respectively. The difference among the three times was significant (P < 0.01, ANOVA). These results suggest that expression of MOPT gene increased from postnatal Day 5 to Day 28, indicating possible involvement in testicular development. The ORF encodes a protein containing 79 amino acid residues. A MORN motif, EGQFKDNMFHGLGTYTFPNG, was identified in the predicted protein sequence of MOPT; function of this motif is unknown. In situ hybridization of 12-week-old wild-type mouse testes using an antisense riboprobe and immuno-gold data indicated MOPT was expressed as a late spermatid and acrosome reaction. This work was supported by BK21 program.

Ultrastructure of spermatogenesis in the free-living marine nematode Anticoma possjetica (Enoplida: Anticomidae)

Abstract- Spermatogenesis of the free-living marine nematode Anticoma possjetica was studied with electron microscopy. The spermatocyte cytoplasm is filled with numerous ribosomes, mitochondria, cisternae of RER and Golgi bodies. After completion of meiosis the nucleus of the spermatids is surrounded by a newly formed nuclear envelope. The first membranous organelles (MO) appear in the early spermatids, in the late spermatid they, together with mitochondria, surround the nucleus. The ribosomes, RER and Golgi bodies are concentrated inside the residual body. The nuclei of immature spermatozoa assume a bullet-like shape and are surrounded by mitochondria and a mass of MO. The mature spermatozoa possess a small anterior pseudopod anchoring them to the spermatheca wall. The spermatozoon cytoplasm is filled with densely packed MO interspersed with mitochondria. During spermatogenesis of A. possjetica, no organelles resembling the fibrous bodies (FB) found in the spermatozoa of other nematodes were observed. The ultrastructural peculiarities of spermatogenesis in A. possjetica differentiate it from many of the other nematodes studied, although important similarities with other enoplids (reconstitution of nuclear envelope) and other Enoplia (late MO formation) are present.