Extent of polyteny in the pericentric heterochromatin of polytene chromosomes of pseudonurse cells of otu (ovarian tumor) mutants of Drosophila melanogaster

Abstract

In the polytene nuclei of germ-line cells (ovarian pseudonurse cells) of Drosophila melanogaster females mutant for otu11 (ovarian tumor), the pericentric heterochromatin is much more abundant than in somatic salivary gland cells. This is due to the degree of heterochromatin compaction (and consequently the level of underreplication) being lower in the nurse cells than in the salivary gland cells. The lower level of compaction probably results in a very low degree of position effect gene inactivation in the ovarian nurse cells.

Hrb27C, Sqd and Otu cooperatively regulategurkenRNA localization and mediate nurse cell chromosome dispersion inDrosophilaoogenesis

“…Nurse cell chromosomes that fail to disperse are also observed in certain alleles of ovarian tumor (otu) (King et al, 1981;King and Storto, 1988;Heino, 1989;Mal'ceva and Zhimulev, 1993;Heino, 1994;Mal'ceva et al, 1995). otu produces two protein isoforms, Otu98 and Otu104, by alternative splicing of a 126 bp exon.…”

DNA replication in nurse cell polytene chromosomes of Drosophila melanogaster otu mutants

“…Our observations are also in line with the results of Hammond and Laird (1985), who demonstrated that during the last endocycle, the regions underreplicated at earlier stages undergo complete replication. This, as well as partial polytenization of pericentric heterochromatin (Mal'ceva and Zhimulev 1993) can be attributed to its earlier replication in NCs as compared to SG polytene chromosomes. However, we must underline that early replication results in only partial polytenization of heterochomatin, with its considerable fraction remaining underreplicated.…”

“…Detailed morphology analysis of NC chromosomes from otu mutants indicated that their banding pattern was very similar, yet not entirely identical to that of SG polytene chromosomes (Heino 1989;Mal'ceva et al 1995;. Notably, pericentric heterochromatin is polytenized in otu NCs significantly more than in SG polytene chromosomes and may form structures with reproducible banding pattern (Mal'ceva and Zhimulev 1993;Koryakov et al 1996;1999;. Moreover, the degree of DNA underreplication and hence the frequency of chromosome breaks are much lower in intercalary heterochromatin regions of NC polytene chromosomes vs those of SGs (Mal'ceva et al 1995;Koryakov et al 2006).…”

Abnormal tissue-dependent polytenization of a block of chromosome 3 pericentric heterochromatin inDrosophila melanogaster

“…Pericentric heterochromatin is almost completely underreplicated in polytene chromosomes of Drosophila (Rudkin, 1965;Berendes and Keyl, 1967;Mulder et al, 1968). Unexpectedly, in otu mutant NC chromosomes, blocks of banded material were present in the heterochromatin region (Mal'ceva and Zhimulev, 1993). In SG chromosomes of SuUR mutants, a reproducible banding pattern appears in the pericentric region of chromosome 3 in place of small lumps of unstructured heterochromatin (Belyaeva et al, 1998;Semeshin et al, 2001).…”

“…In D. melanogaster, mutation otu causes formation of polytene chromosomes in NCs (King et al, 1981), which show greater polytenization of heterochromatic sequences than in SGs (Mal'ceva and Zhimulev, 1993;Koryakov et al, 1996).…”