speck, first identified in Drosophila melanogaster in 1910, is encoded by the Arylalkalamine N-acetyltransferase (AANAT1) gene

Abstract

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 115 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.

Extracellular matrix protein N-glycosylation mediates immune self-tolerance inDrosophila melanogaster

“…Since that time, the Drosophila genome has been sequenced and annotated, the protein products of many genes in the mapped region have been characterized, and mutant strains have been developed for many of these genes. Furthermore, numerous molecularly defined chromosomal aberration collections have become available in Drosophila (68-72), which enables fine scale mapping of many classic mutations that had not been previously localized to the genome (73). We took a candidate gene approach as well as a mapping approach that makes use of complementation testing using defined genomic deletions and duplications.…”

AANAT1 functions in astrocytes to regulate sleep homeostasis

“…In Drosophila , mutants of arylalkylamine N-acetyltransferase 1 ( AANAT1 lo ) were reported to have normal baseline amounts of sleep and motor activity, but increased recovery sleep (‘rebound’) following deprivation ( Shaw et al, 2000 ). AANAT1 corresponds to speck , a long-known mutation characterized by a darkly pigmented region at the wing hinge ( Spana et al, 2020 ). AANAT1 can acetylate and inactivate monoamines in vitro ( Hintermann et al, 1995 ), but the role of AANAT1 in vivo remains poorly understood.…”

Arylalkalamine N‐acetyltransferase‐1 functions on cuticle pigmentation in the yellow fever mosquito, Aedes aegypti

“…Because melatonin regulates circadian rhythms, aaNAT, also called Timezyme has been intensively studied in vertebrates with the aim of understanding its role in the biological event (Chong et al ., 2000; Klein, 2007; Velarde et al ., 2010). Studies of aaNATs have been focused on cuticle pigmentation in insects (Zhan et al ., 2010; Noh et al ., 2016; Spana et al ., 2020). Early studies of the pigmentation pathway were performed in Drosophila melanogaster ; the pathway begins with the hydroxylation of tyrosine by tyrosine hydroxylase (encoded by the pale gene) (Neckameyer & White, 1993) to form dopa which is further modified by dopa decarboxylase (encoded by the Ddc gene) (Hirsh & Davidson, 1981; Han et al ., 2010) to form dopamine.…”

“…Early studies of the pigmentation pathway were performed in Drosophila melanogaster ; the pathway begins with the hydroxylation of tyrosine by tyrosine hydroxylase (encoded by the pale gene) (Neckameyer & White, 1993) to form dopa which is further modified by dopa decarboxylase (encoded by the Ddc gene) (Hirsh & Davidson, 1981; Han et al ., 2010) to form dopamine. From dopamine, the pigmentation pathway branches onto three routes: the melanin pathway, the N‐β‐alanyldopamine sclerotin pathway and the N‐acetyldopamine (NADA) sclerotin pathway (True et al ., 2005; Liao et al ., 2018; Spana et al ., 2020). The aaNAT was only involved in the final route, NADA sclerotin pathway where the dopamine is converted to NADA by the activity of aaNAT1 (encoded by the speck gene).…”

“…The aaNAT was only involved in the final route, NADA sclerotin pathway where the dopamine is converted to NADA by the activity of aaNAT1 (encoded by the speck gene). NADA secreted into the extracellular space may also be converted to a quinone by the role of straw gene and used in the formation of colorless NADA sclerotin (Spana et al ., 2020).…”