ABSTRACT
A subtractive-hybridization technique, combined with differential screenings and subsequent whole mount in situ hybridization (ISH) reactions, was used to isolate novel cDNA clones representing developmentally-regulated genes of carp. Small-scale differential screenings of an oocyte and a segmentation-stage cDNA library using oocyte-specific and segmentation stage-specific enriched probes, yielded 75 positive clones. ISH screening showed that 65% (15) of the oocyte-stage clones and 50% (26) of the segmentation-stage clones were indeed stage-specific. Partial sequence analysis suggests that approximately 65% of the 41 stage-specific clones represent novel genes. In addition, an Otxl clone was isolated. Two novel clones and the Otxl clone are of special interest for developmental studies. The clones represent genes that are locally expressed during embryonic development. The expression patterns of Otxl and one of the novel clones suggest functions in specification of the anterior-posterior axis. The three clones provide molecular markers for the study of gastrulation and the patterning of the a-p axis in teleosts.
ABSTRACT
Carp embryos were dechorionated and their early development was studied in the presence or absence of a-amanitin. Cleavage and the formation of the enveloping layer and yolk syncytial layer were not influenced by the drug. However, a-amanitin largely blocked epiboly which started 6 h after fertilization in controls. Involution of deep cells, taking place during gastrulation movements, appeared to be blocked to a lesser degree. This might reflect differences in the degree to which maternal transcripts influence these developmental steps.
