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Figure 6 | BMC Developmental Biology

Figure 6

From: Characterization, developmental expression and evolutionary features of the huntingtin gene in the amphioxus Branchiostoma floridae

Figure 6

Schematic diagram of a B. floridae larva showing some of the details useful for following AmphiHtt expression. Upper panel: Longitudinal view of an amphioxus larva (green: nervous system; yellow: notochord; pink: gut endoderm). The central nervous system has homologues of at least three major vertebrate brain subdivisions: the fore-, mid-, and hindbrain. The cerebral vesicle (cv) can be subdivided into rostral (A, anterior) and caudal (P, posterior) parts, and only corresponds to the diencephalic region of the vertebrate forebrain (FB) because it lacks of a telencephalic region [43]. The anterior part of the cerebral vesicle consists of the frontal eye complex (fe), characterised by a cluster of pigmented epithelial cells (pigment cup) and four rows of neurons [44]. The posterior part begins with the infundibular cells (if) that are responsible for producing Reissner's fibres in amphioxus and it is homologous to a vertebrate diencephalic region corresponding to the subcommisural organ [45]. Beginning near the front of the posterior cerebral vesicle, the lamellar body (lb), a putative homologue of the vertebrate pineal eye (epiphysis) [43], is located dorsally. This is followed by a midbrain-like region (MB), including the tectal zone extending from the posterior part of the lamellar body to the anterior part of the primary motor centre (pmc), and then a hindbrain-like region (HB), that starts from the posterior part of the pmc and extends caudally over the first pigment spot (ps), has an uncertain posterior limit (?) [46,47]. Some non neuronal structures are indicated: hld, Hatchek's left diverticulum; s, somites; tb, tail-bud. A grey triangle indicates the expression gradient of AmphiHtt from the most anterior part to approximately two-thirds of the neural tube. Lower panel: Median cross section of an amphioxus larval body showing the dorso-ventral organisation of the major structures: nt, neural tube; n, notochord; e, endoderm; s, somites. The neural tube is positioned dorsally to the notochord (n) and somites (s) are positioned laterally to the neural tube (nt).

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