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Un cambio relativo en la ubicación cloacal reubica los genitales externos en la evolución del amniote
Patrick Tschopp1, Emma Sherratt2, Thomas J Sanger2
1Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.
Nature
|November 11, 2014
Resumen
La evolución de los genitales externos en los vertebrados muestra un cambio en los orígenes del desarrollo. En algunas especies, las extremidades y los genitales comparten un punto de partida de desarrollo común, lo que sugiere un origen ancestral parecido a una extremidad.
Área de la Ciencia:
- Biología del desarrollo Biología del desarrollo.
- Biología evolutiva Biología evolutiva.
- Anatomía comparada y anatomía comparada.
Sus antecedentes:
- La terrestrización de los vertebrados requirió adaptaciones en la locomoción y la reproducción.
- La transición de las aletas a los miembros está bien estudiada, pero los orígenes de los genitales externos siguen sin estar claros.
- Las similitudes en la expresión génica insinúan un vínculo evolutivo entre las extremidades y los genitales, pero se desconocen los mecanismos de desarrollo.
Objetivo del estudio:
- Investigar los orígenes del desarrollo y la evolución de los genitales externos.
- Para determinar si las extremidades y los genitales comparten vías de desarrollo comunes.
- Aclarar los mecanismos que impulsan la diversificación del desarrollo genital.
Principales métodos:
- Tomografía microcomputada (micro-CT) para imágenes de alta resolución.
- El rastreo del linaje en tres grupos de amniotas (lagartos, serpientes, ratones).
- Secuenciación de ARN (RNA-seq) para el perfil de transcripción.
Principales resultados:
- El desarrollo de los genitales externos ha evolucionado, con algunos taxones que muestran un primordio compartido entre las extremidades y los genitales.
- En los escamados, los genitales se desarrollan a partir de brotes de las extremidades posteriores; en los ratones, surgen del mesénquima ventral y de la cola.
- La posición de la cloaca (centro organizador de los genitales) influye en el reclutamiento celular para el crecimiento de los genitales, con respuestas de señalización conservadas.
Conclusiones:
- La condición ancestral para el desarrollo de los genitales externos es probablemente similar a la de las extremidades.
- Un cambio en la posición de la cloaca durante la evolución alteró el desarrollo genital en los mamíferos.
- El desarrollo genital de los mamíferos conserva los circuitos moleculares de las extremidades ancestrales debido a un origen evolutivo compartido.
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