The role of the 5′ HoxA genes in the development of the hindgut, vent, and a novel sphincter in a derived teleost (bluebanded goby, Lythrypnus dalli)

• Published in: Journal of experimental zoology. Part B, Molecular and developmental evolution Vol. 340; no. 8; pp. 518 - 530
• Main Authors: Crow, Karen D., Sadakian, Ara, Kaslly, Noelle A.
• Format: Journal Article
• Language: English
• Published: United States 01.12.2023
• Subjects: Animals; Fishes; goby; gut development; Homeodomain Proteins - genetics; Homeodomain Proteins - metabolism; HoxA11; HoxA13; novel; Perciformes - metabolism; sphincter; HoxA11; HoxA13; gut development; sphincter; novel; goby
• ISSN: 1552-5007; 1552-5015
• DOI: 10.1002/jez.b.22982

Unique expression patterns of the 5′ HoxA genes are associated with the evolution and development of novel features including claspers in cartilaginous fishes, modified pectoral fins in batoids, and the yolk sac extension in Cypriniformes. Here, we demonstrate a role for HoxA11a and HoxA13a in demarcating the hindgut in fishes of the family Gobiidae, including a novel sphincter called the intestinal rectal sphincter (IRS). Disruption of 5′ HoxA expression, via manipulation of retinoic acid signaling, results in failure of the IRS and/or vent to develop. Furthermore, exposure to HoxA disruptors alters 5′ HoxA expression, in association with developmental phenotypes, demonstrating a functional link between 5′ HoxA expression and development of a novel feature in the bluebanded goby, Lythrypnus dalli. Interruption of gut development after exposure to HoxA disruptors in the bluebanded goby. HoxA11a and Hox13a (HoxA) are expressed in specific domains in the hindgut and vent of bluebanded gobies (Lythrypnus dalli) that specify three distinct sphincters: the intestinal rectal sphincter (IRS), hindgut sphincter and the vent sphincter. HoxA was disrupted by manipulating retinoic acid (RA) signaling during gut development in five replicate clutches of goby embryos. There were significant differences in the proportion of embryos that developed an IRS and vent after exposure to two HoxA disruptors compared with controls. Significant differences are indicated by * when p < .05. Post hoc Tukey test was performed to indicate which treatments were significantly different for each phenotype. Standard error (SE) bars are shown for each treatment per trait. Green stars represent significant disruption when treated with RA; orange stars represent significant disruption when treated with disulfiram. HIGHLIGHTS Disruption of HoxA11a and HoxA13a is associated with modified expression patterns and loss of a novel sphincter, establishing a functional link between 5' HoxA expression and development of a novel feature that is unique the family Gobiidae.