Hox gene colinear expression in the avian medulla oblongata is correlated with pseudorhombomeric domains |
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Authors: | Marín Faustino Aroca Pilar Puelles Luis |
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Affiliation: | Department of Human Anatomy and Psychobiology, School of Medicine, University of Murcia, CIBER de Enfermedades Raras (CIBERER), Instituto Universitario de Envejecimiento, E-30100 Murcia, Spain |
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Abstract: | The medulla oblongata (or caudal hindbrain) is not overtly segmented, since it lacks observable interrhombomeric boundaries. However, quail-chick fate maps showed that it is formed by 5 pseudorhombomeres (r7-r11) which were empirically found to be delimited consistently at planes crossing through adjacent somites (Cambronero and Puelles, 2000). We aimed to reexamine the possible segmentation or rostrocaudal regionalisation of this brain region attending to molecular criteria. To this end, we studied the expression of Hox genes from groups 3 to 7 correlative to the differentiating nuclei of the medulla oblongata. Our results show that these genes are differentially expressed in the mature medulla oblongata, displaying instances of typical antero-posterior (3′ to 5′) Hox colinearity. The different sensory and motor columns, as well as the reticular formation, appear rostrocaudally regionalised according to spaced steps in their Hox expression pattern. The anterior limits of the respective expression domains largely fit boundaries defined between the experimental pseudorhombomeres. Therefore the medulla oblongata shows a Hox-related rostrocaudal molecular regionalisation comparable to that found among rhombomeres, and numerically consistent with the pseudorhombomere list. This suggests that medullary pseudorhombomeres share some AP patterning mechanisms with the rhombomeres present in the rostral, overtly-segmented hindbrain, irrespective of variant boundary properties. |
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Keywords: | 6, abducens nucleus 6n, abducens nerve 8cn, cochlear nerve 9, glossopharyngeal dorsal motor nucleus 9n, glossopharyngeal nerve 10, dorsal motor nucleus of the vagus 10n, vagus nerve 11, accessory nerve nucleus 12, hypoglossal nucleus 11, ambiguus nucleus Amb, ambiguus nucleus Ang, angular cochlear nucleus dcn, dorsal column nuclei Gi, gigantocellular nucleus Gu, gustatory nucleus IOD, inferior olivary nucleus, dorsal lamina IOV, inferior olivary nucleus, ventral lamina IRt, intermediate reticular nucleus IZ, intermediate zone LVeD, lateral vestibular nucleus, dorsal part LVeV, lateral vestibular nucleus, ventral part MCC, magnocellular cochlear nucleus mlf, medial longitudinal fasciculus MSO, medial superior olivary nucleus MVe, medial vesticbular nucleus PCRt, parvicellar storm Pe, periventricllar stratum PMn, paramedian reticular nucleus Pn, pontine nuclei Pr, prepositus nucleus r, rhombomere RF, retrofacial nucleus RO, raphe obscurus RPa, raphe pallidus Rt, reticular formation RVL, rostroventrolateral reticular nucleus Sol, nucleus sol, solitary tract Sp5C, spinal trigminal nucleus, caudal part SP5I, spinal trigminal nucleus SpVe, spinal vestibular nucleus vc, ventral column of the spinal cord VH, ventral horn of spinal cord xc, cochlear decussation xsol, decussation of the solitary tract xv, vestibular commissure |
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