Search

Optimal cardiac function requires appropriate contractile proteins in each heart chamber. Atria require slow myosins to act as variable reservoirs, while ventricles demand fast myosin for swift pumping functions. Hence, myosin is under chamber-biased cis-regulatory control to achieve this functional distribution. Failure in proper regulation of myosin genes can lead to severe congenital heart dysfunction. The precise regulatory input leading to cardiac chamber-biased expression remains uncharted. To address this, we computationally and molecularly dissected the quail Slow Myosin Heavy Chain III (SMyHC III) promoter that drives specific gene expression to the atria to uncover the regulatory information leading to chamber expression and understand their evolutionary origins. We show that SMyHC III gene states are autonomously orchestrated by a complex nuclear receptor cis-regulatory element (cNRE), a 32- bp sequence with hexanucleotide binding repeats. Using in vivo transgenic assays in zebrafish and mouse models, we demonstrate that preferential atrial expression is achieved by the combinatorial regulatory input composed of atrial activation motifs and ventricular repression motifs. Through comparative genomics, we provide evidence that the cNRE emerged from an endogenous viral element, most likely through infection of an ancestral host germline. Our study reveals an evolutionary pathway to cardiac chamber-specific expression.

A evolução da morfologia serpentiforme, caracterizada simultaneamente pelo alongamento do corpo e pela redução de membros locomotores, ocorreu repetidas vezes durante a história evolutiva de Squamata. Alterações em parâmetros morfológicos relacionados à locomoção de um organismo afetam diretamente seu desempenho em atividades essenciais à sobrevivência e à produção de descendentes e, portanto, espera-se que estejam relacionadas a adaptações a características do ambiente ocupado por ele. Estudos ecomorfológicos sugerem que o surgimento de morfologias serpentiformes em Squamata ocorreu frequentemente associado à ocupação de diferentes habitats, resultando em duas ecoformas distintas: espécies epígeas, que geralmente possuem tronco e cauda alongados, e espécies fossoriais, que geralmente possuem tronco alongado e cauda curta. O objetivo deste trabalho foi investigar a existência de relações evolutivas entre ecologia e aspectos morfológicos, como alongamento do corpo e redução dos membros, em espécies de lagartos neotropicais da família Gymnophthalmidae, avaliando como essas mudanças influenciam seu desempenho locomotor. Evolution of snakelike morphology, characterized by both body elongationand and limb reduction, has ocurred several times during evolutionary history of Squamata. Changes in morphological parameters related to locomotion directly affect organismal performance in several activities that are crucial to survival and descendent produciton. Therefore, these morphological changes are expected to be adaptive to the environment where the organism occurs. Ecomorphological studies suggests that the evolution of snakelike morphologies in Squamata ocurred frequently associated to the ocupation of different habitats, giving rise to two distinct ecomorphs: grass-swimming species, which generally have elongation of trunk and tail, and fossorial species, which generally have elongation of trunk and short tail. The aim of the present study was to investigate the existence of evolutionary relationships between ecology and morphological aspects like body elongation and limb reduction in species of neo-tropical lizard family Gymnophthalmidae, evaluating how these evolutionary changes affect locomotor performance.