Fluorescent in situ hybridization analyses of human oocytes in trisomy 18 and 21
- Univ. of Washington School of Medicine, Seattle, WA (United States)
The commonly accepted view of synapsis is that only 2 homologues can synapse at any one site and that this restriction applies to polyploids as well. However, triple synapsis has been observed is some triploid plants and in triploid chicken. In humans, triple synapsis of the long arm of chromosome 21 was detected in sperm of a trisomic 21 individual. More recently, studies of oocytes from trisomic 21 and 18 fetuses also indicated extensive triple synapsis along the entire length of the chromosomes. To further investigate this question, we undertook an evaluation of trivalent synapsis in fetal oocytes from 2 trisomic 21 and 2 trisomic 18 fetuses using fluorescent in situ hybridization (FISH) with whole chromosome probes. Oocytes were hybridized with whole chromosome probes obtained from ONCOR, Inc. after fixation with methanol and acetic acid. Slides were scored for the distribution of prophase stages, hybridization efficiency, and hybridization characteristics of chromosomes 18 and 21 in the trisomic 18 and 21 fetuses respectively. Fifty-eight per cent (379/650) of pachytenes analyzed for chromosome 18 contained a conspicous trivalent and 319 (48%) of these nuclei contained a single, thick, continuous fluorescent signal consistent with complete triple synapsis along the entire length of all 3 chromosomes. Sixteen per cent (104/650) of pachytene contained 2 signals consistent with a bivalent and a univalent, and 9 cells contained 3 thin signals consistent with asynapsis of all 3 chromosomes. The remaining 158 pachytenes had unusual pairing configurations that we could not classify, but they most likely represent trivalents with partial pairing between different homologues. In the 2 trisomic 21 fetuses, the majority (143/232) of pachytenes also contained one signal while only 52 cells contained a bivalent and univalent. Five cells contained 3 separate signals. These results confirm the existence of triple synapsis in human meiosis.
- OSTI ID:
- 133436
- Report Number(s):
- CONF-941009-; ISSN 0002-9297; TRN: 95:005313-0164
- Journal Information:
- American Journal of Human Genetics, Vol. 55, Issue Suppl.3; Conference: 44. annual meeting of the American Society of Human Genetics, Montreal (Canada), 18-22 Oct 1994; Other Information: PBD: Sep 1994
- Country of Publication:
- United States
- Language:
- English
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