The pigmentation mutation speck is a commonly used recombination marker characterized by a darkly pigmented region at the wing hinge. Identified in 1910 by Thomas Hunt Morgan, speck was characterized by Sturtevant as the most "workable" mutant in the rightmost region of the second chromosome and eventually localized to 2-107.0 and 60C1-2. Though the first speck mutation was isolated over 110 years ago, speck is still not associated with any gene. Here, as part of an undergraduate-led research effort, we show that speck is encoded by the Arylalkylamine N-acetyltransferase 1 (AANAT1) gene. Both alleles from the Morgan lab contain a retrotransposon in exon 1 of the RB transcript of the AANAT1 gene. We have also identified a new insertion allele and generated multiple deletion alleles in AANAT1 that all give a strong speck phenotype. In addition, expression of AANAT1 RNAi constructs either ubiquitously or in the dorsal portion of the developing wing generates a similar speck phenotype. We find that speck alleles have additional phenotypes, including ectopic pigmentation in the posterior pupal case, leg joints, cuticular sutures and overall body color. We propose that the acetylated dopamine generated by AANAT1 decreases the dopamine pool available for melanin production. When AANAT1 function is decreased, the excess dopamine enters the melanin pathway to generate the speck phenotype.

色素突变斑点是一种常用的重组标记，其特征是机翼铰链处有深色色素区域。 1910 年，Thomas Hunt Morgan 发现了Speck ，Sturtevant 将其定性为第二染色体最右侧区域中最“可行”的突变体，并最终定位于 2-107.0 和 60C1-2。尽管第一个斑点突变在 110 多年前就被分离出来，但斑点仍然与任何基因无关。在这里，作为本科生主导的研究工作的一部分，我们证明斑点是由芳基烷基胺 N-乙酰转移酶 1 ( AANAT1 ) 基因编码的。 Morgan 实验室的两个等位基因在AANAT1基因 RB 转录物的外显子 1 中都含有逆转录转座子。我们还在AANAT1中鉴定了一个新的插入等位基因并生成了多个删除等位基因，所有这些都给出了强斑点表型。此外， AANAT1 RNAi 构建体的表达要么普遍存在，要么在发育中的翅膀的背部部分产生类似的斑点表型。我们发现斑点等位基因具有额外的表型，包括蛹后部、腿部关节、角质缝线和整体身体颜色的异位色素沉着。我们认为AANAT1产生的乙酰化多巴胺减少了可用于黑色素产生的多巴胺库。当AANAT1功能下降时，过量的多巴胺进入黑色素途径，产生斑点表型。