Campbell S D, Duttaroy A, Katzen A L, Chovnick A
Molecular and Cell Biology, University of Connecticut, Storrs 06269-2131.
Genetics. 1991 Feb;127(2):367-80. doi: 10.1093/genetics/127.2.367.
Viable mutants of the scalloped gene (sd) of Drosophila melanogaster exhibit defects that can include gapping of the wing margin and ectopic bristle formation on the wing. Lethal sd alleles characterized in the present study now implicate this gene in a genetic function essential for normal development. In order to further characterize the developmental role of this gene, we have undertaken to clone and characterize the region where sd maps. A P[ry+] transposon insertion at 13F associated with sd[ry+2216] served as the starting point for a 42-kb chromosomal walk. Molecular lesions associated with viable and lethal sd alleles were characterized by genomic hybridization analysis as a means of defining the extent of the gene. DNA rearrangements associated with 11 viable sd alleles map to a 2-kb interval which appears to be a "hot spot" for P element activity. Four of five recessive lethal sd mutations were mapped by denaturing gradient gel electrophoresis to a region 12-14 kb away from the region of viable lesions. In a sd+ genotype, at least two structurally related and developmentally regulated transcripts hybridize to the genomic region where several sd lethal alleles have been localized. A viable mutation, sd58, used for comparison in the transcript analysis, makes at least two slightly smaller transcripts that also hybridize to this region. Preliminary analysis of cDNA clones has identified three structurally related transcripts that hybridize to this genomic region. The 5' end of these transcripts extends into the 2-kb genomic region wherein DNA rearrangements were seen in the P element rearrangements. We favor the view that the transcripts represented by these cDNA clones are products of the sd gene. If this is true, the sd gene would include genomic sequences extending over at least 14 kb of the described chromosomal walk, and would appear to be subject to alternative splicing.
黑腹果蝇扇形基因（sd）的存活突变体表现出的缺陷包括翅缘缺口和翅上异位刚毛形成。本研究中鉴定的致死性sd等位基因表明该基因在正常发育所必需的遗传功能中发挥作用。为了进一步阐明该基因在发育中的作用，我们着手克隆并鉴定sd基因所在的区域。与sd[ry+2216]相关的位于13F的P[ry+]转座子插入作为42kb染色体步移的起点。通过基因组杂交分析鉴定与存活和致死性sd等位基因相关的分子损伤，以此确定基因的范围。与11个存活sd等位基因相关的DNA重排定位于一个2kb的区间，该区间似乎是P元件活性的“热点”。通过变性梯度凝胶电泳将5个隐性致死性sd突变中的4个定位于距存活损伤区域12 - 14kb的区域。在sd+基因型中，至少有两个结构相关且受发育调控的转录本与已定位多个sd致死等位基因的基因组区域杂交。用于转录本分析比较的存活突变体sd58产生至少两个略小的转录本，它们也与该区域杂交。对cDNA克隆的初步分析已鉴定出三个与该基因组区域杂交的结构相关转录本。这些转录本的5'端延伸到在P元件重排中观察到DNA重排的2kb基因组区域。我们倾向于认为这些cDNA克隆代表的转录本是sd基因的产物。如果这是真的，sd基因将包括在所描述的染色体步移中至少延伸14kb的基因组序列，并且似乎存在可变剪接。
