Category Archives: Ovary

Large-Scale Generation and Analysis of Expressed Sequence Tags: DISCUSSION(12)

DISCUSSION(12)

Five contigs (contig 288 [ferritin, heavy polypeptide], contig 430 [monooxygenase], contig 64 [selenoprotein P-like protein], contig 756 [inhibin a chain], and contig 34 [vimentin]) had cDNAs that were predominately derived from prepubertal ovaries (pputal library). The prepubertal ovaries used to construct the pputal library contained antral follicles. Each of the five contigs was among the largest contigs in the collective follicle libraries (Table 5). The observed frequencies of cDNA in the pputal library therefore supported the sequencing data from the follicle libraries (Table 5).

Large-Scale Generation and Analysis of Expressed Sequence Tags: DISCUSSION(11)

The ovary then undergoes a protracted period of follicular growth before puberty. Three genes had contigs that were highly represented in either fetal or neonatal ovary (P < 0.001; contig 33 [ATP synthase A chain], contig 161 [cytochrome c oxidase III], and contig 412 [collagen, type III, a1]) (Table 7). The fetal ovary is densely packed with oocytes, and oocytes have a large number of mitochondria. Thus, the high frequency of ATP synthase and cytochrome c oxidase in the pfeto libraries may reflect the preponderance of mitochondria in developing oocytes.

Large-Scale Generation and Analysis of Expressed Sequence Tags: DISCUSSION(10)

DISCUSSION(10)

Nexin-1 mRNA decreases after the LH surge. Thus, the decrease in a specific protease inhibitor may facilitate ovulation. Translationally controlled tumor protein was recently implicated as a protein that binds elongation factor eEF1A during the elongation step of protein synthesis. The abundance of TCTP cDNA in follicle libraries (Tables 5 and 6) highlights the importance of protein synthesis during follicular development. The presence of collagen a2 (I) in pd12fol may reflect the relative abundance of specific collagen subunits in follicles versus corpora lu-tea. The two contigs classified as unknown should be investigated further as genes controlling unique aspects of follicular development.

Large-Scale Generation and Analysis of Expressed Sequence Tags: DISCUSSION(9)

Thus, PSP-94 may control cell growth and development either through an indirect effect on immune cells or through a direct effect on luteal cells themselves. We examined PSP-94 in cow and pig corpus luteum and found that the mRNA was only expressed in pig corpus luteum (unpublished observations). Furthermore, the mRNA was maximally expressed in midcycle corpora lutea. Thus, the porcine corpus luteum may be unique from the corpus luteum of other species in that it specifically expresses PSP-94 (Fig. 5). The highly specific expression of PSP-94 mRNA suggests a unique role for this protein in porcine corpus luteum.

Large-Scale Generation and Analysis of Expressed Sequence Tags: DISCUSSION(8)

DISCUSSION(8)

Greater StAR mRNA within corpora lutea relative to follicles has also been found in porcine ovary. The difference in cDNA frequency may reflect the greater mitochondrial density as well as greater steroidogenic capacity of corpus luteum relative to follicle. Tissue inhibitors of metallopro-teinases play a role in remodeling of the extracellular matrix. The expression of TIMP-1 mRNA increases during late preovulatory development and increases further within the corpus luteum. To our knowledge, specific expression of CYP1B1 (a P450 enzyme involved in steroid metabolism) in corpus luteum has not been previously reported.

Large-Scale Generation and Analysis of Expressed Sequence Tags: DISCUSSION(7)

A clear increase in ferritin cDNA was noted within the p6mm library, and to our knowledge, changes in ferritin mRNA have not been previously reported in preovulatory follicles. Iron is required for coordinating the heme within P450 enzymes, which is a class of enzymes that includes those involved in steroidogenesis. Ferritin sequesters and stores intracellular iron in a nontoxic form. The increase in ferritin in preovulatory follicles may play an important role in iron homeostasis during the preovulatory period.

Large-Scale Generation and Analysis of Expressed Sequence Tags: DISCUSSION(6)

DISCUSSION(6)

The cDNA sequence is found within the TIGR database but, nonetheless, cannot be tied to any known gene. The identity and function of this unknown protein that is increased in large porcine follicles is a potential subject for future investigations.

Contig 288 (ferritin, heavy polypeptide), contig 273 (prostaglandin F synthase 1), and contig 756 (inhibin a) were specifically increased in the p6mm library at P < 0.001.

Large-Scale Generation and Analysis of Expressed Sequence Tags: DISCUSSION(5)

Five contigs had cDNA clone frequencies that increased in the collective p6mm and p8mm libraries (contig 2 [elongation factor 1a], contig 1 [cytochrome c oxidase], contig 160 [cytochrome b], contig 36 [glutathione 5-transferase], and contig 18 [unknown]). The physiological basis for the observed changes in gene frequency is open to further scientific investigation. The increase in elongation factor 1 a mRNA and cytochrome c oxidase mRNA may reflect an increase in protein synthesis and energy metabolism, respectively, in large follicles.

Large-Scale Generation and Analysis of Expressed Sequence Tags: DISCUSSION(4)

DISCUSSION(4)

For this reason, the frequency of each cDNA from each library was counted. Analysis of the cDNA frequency across different libraries suggested differential patterns of expression within different-size follicles (diameter, 2-8 mm) (Table 5), between follicles and corpora lutea (Table 6), and across developmental time-points (fetal, neonatal, and prepubertal ovary) (Table 7). The expression of selected genes was consistent with the frequencies of their respective cDNA in the individual libraries (analyzed by RP assay or Northern blot) (Fig. 5).

Large-Scale Generation and Analysis of Expressed Sequence Tags: DISCUSSION(3)

Thus, the bulk of the mRNA within an ovarian cell encodes genes that are involved in the intracellular activities that are not unique to ovarian cells (metabolism, protein synthesis, etc.), and only a small percentage of the major cDNA species appeared to be specific to reproductive tissues. Reproductive genes with a high expression level (high frequency of sequenced cDNA) included inhibin a and PSP-94. The abundance of cDNA for these two reproductive genes in ovary is unusual, because most other genes previously associated with ovarian function were found in relatively low numbers.

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