RESUMEN
The enteric nervous system arises predominantly from vagal level neural crest cells that migrate into and along the developing gut. As the neural crest-derived cells migrate within the gut, a subpopulation begins to differentiate into enteric neurons. Here, we show that the differentiation of neural crest-derived cells into enteric neurons is delayed in L1-deficient mice, compared with littermate controls. However, glial cell differentiation is not affected in L1-deficient mice. These mice also show a delay in the differentiation of a neurotransmitter-specific subtype of enteric neuron within the gastrointestinal tract. Together, these results suggest a role for the cell adhesion molecule, L1, in the differentiation of neural crest-derived cells into enteric neurons within the developing enteric nervous system.
Asunto(s)
Diferenciación Celular , Sistema Digestivo/embriología , Sistema Digestivo/metabolismo , Sistema Nervioso Entérico/embriología , Sistema Nervioso Entérico/metabolismo , Molécula L1 de Adhesión de Célula Nerviosa/metabolismo , Neuronas/citología , Animales , Muerte Celular , Proliferación Celular , Sistema Digestivo/citología , Sistema Nervioso Entérico/citología , Regulación del Desarrollo de la Expresión Génica , Ratones , Molécula L1 de Adhesión de Célula Nerviosa/deficiencia , Molécula L1 de Adhesión de Célula Nerviosa/genética , Neuronas/metabolismoRESUMEN
The enteric nervous system arises predominantly from vagal level neural crest cells that migrate into the foregut and then colonize the entire length of the gastrointestinal tract. Previous studies have demonstrated that glial cell line-derived neurotrophic factor (GDNF) promotes the migration of enteric neural crest-derived cells (ENCs) in vitro, but a role for GDNF in the migration of ENCs in vivo has yet to be demonstrated. In this study, the effects of Gdnf haploinsufficiency on ENC rate of migration and number during mid embryonic development were examined. Although the entire gut of embryonic Gdnf(+/-) mice was colonized, a significant delay in the migration of ENCs along the embryonic hindgut was found. However, significant effects of Gdnf haploinsufficiency on ENC number were detected before the stage at which migration defects were first evident. As previous studies have shown a relationship between ENC number and migration, the effects of Gdnf haploinsufficiency on migration may be due to an indirect effect on cell number and/or a direct effect of GDNF on ENC migration. Gdnf haploinsufficiency did not cause any detectable change in the rate of neuronal differentiation of ENCs.
Asunto(s)
Movimiento Celular/genética , Sistema Nervioso Entérico/embriología , Factor Neurotrófico Derivado de la Línea Celular Glial/genética , Cresta Neural/fisiología , Animales , Diferenciación Celular , Sistema Nervioso Entérico/citología , Sistema Nervioso Entérico/fisiología , Femenino , Tracto Gastrointestinal/embriología , Tracto Gastrointestinal/fisiología , Factor Neurotrófico Derivado de la Línea Celular Glial/metabolismo , Proteínas de Homeodominio/genética , Proteínas de Homeodominio/metabolismo , Inmunohistoquímica , Masculino , Ratones , Ratones Endogámicos C57BL , Cresta Neural/citología , Cresta Neural/embriología , Factores de Transcripción/genética , Factores de Transcripción/metabolismoRESUMEN
BACKGROUND & AIMS: During development, the enteric nervous system is derived from neural crest cells that emigrate from the hindbrain, enter the foregut, and colonize the gut. Defects in neural crest migration can result in intestinal aganglionosis. Hirschsprung's disease (congenital aganglionosis) is a human condition in which enteric neurons are absent from the distal bowel. A number of clinical studies have implicated the cell adhesion molecule L1 in Hirschsprung's disease. We examined the role of L1 in the migration of neural crest cells through the developing mouse gut. METHODS: A variety of in vitro and in vivo assays were used to examine: (1) the effect of L1 blocking antibodies or exogenous soluble L1 protein known to compromise L1 function on the rate of crest cell migration, (2) the effect of blocking L1 activity on the dynamic behavior of crest cells using time-lapse microscopy, and (3) whether the colonization of the gut by crest cells in L1-deficient mice differs from control mice. RESULTS: We show that L1 is expressed by neural crest cells as they colonize the gut. Perturbation studies show that disrupting L1 activity retards neural crest migration and increases the number of solitary neural crest cells. L1-deficient mice show a small but significant reduction in neural crest cell migration at early developmental stages, but the entire gastrointestinal tract is colonized. CONCLUSIONS: L1 is important for the migration of neural crest cells through the developing gut and is likely to be involved in the etiology of Hirschsprung's disease.