Figure 13.

Two mouse brain sagittal sections reacted genoarchitectonically to visualize prethalamic and hypothalamic subdomains in a broader forebrain context (particularly diencephalic). Material extracted and slightly modified from (Puelles L. et al., 2012a) no copyright permission required). (A) Is a E16.5 mouse embryo sagittal section showing weak Dlx5/6-LacZ blue reaction at sites of Dlx gene expression e.g., the hypothalamic subparaventricular area (spa), continuous caudally with the prethalamic zona incerta area (zi), the latter being also continuous over the Nkx2.2-positive shell domains of the zona limitans (compare Figure 5C) with further alar areas always next to the basal plate down to the midbrain (this band coincides with sites producing GABAergic neurons). Calretinin immunoreaction was combined in (A) (brown reaction), to highlight the prethalamic eminence subregion (pthe) as well as some partial basal plate patterns across hp1, dp3, and dp2. The dash lines mark interprosomeric boundaries running from roof to floor. Note retroflex tract (rf) and posterior commissure (pc) as boundary-related landmarks. The alar prethalamus appears accordingly divided into three dorsoventral subdomains, namely the prethalamic eminence (pthe), the subjacent area occupied by the major prethalamic derivatives (reticular nucleus, and the pregeniculate and subgeniculate visual centers—marked “pth”) and the zona incerta area (zi). Note the underlying prethalamic tegmentum (separated by the red alar-basal boundary) is also divided into three dorsoventral subdomains (longitudinal dash lines), which also extend throughout the whole forebrain. The hypothalamic alar plate, in contrast, is divided only into two dorsoventral zones, the paraventricular area (pa) and the subparaventricular area (spa). The pa has a sharp molecular boundary with the alar prethalamus (pth); see also (B). It is larger dorsoventrally within hp1, whereas the spa is larger within hp2 (peduncular vs. terminal hypothalamus; compare Figure 10). The basal plate hypothalamic territory is divided dorsoventrally in three longitudinal zones: tu/rtu (tuberal and retrotuberal; this expands rostralwards into the acroterminal area; check Figure 10), pm/prm (perimamillary/periretromamillary), and m/rm (mamillary and retromamillary). The preoptic area (poa) falls inside the telencephalic subpallium, jointly with the ganglionic eminences (here only the mge is seen) and the subpallial septum (se). (B) This sagittal section of an adult mouse brain shows hypothalamic molecular domains complementary to those labeled in (A). The blue signal corresponds to Otp-LacZ reaction present in neurons that express the Otp gene. This signal is mainly characteristic of the oxytocin/vasopressin neurons of the hypophysiotropic magnocellular paraventricular nucleus. Here we see even more clearly than in the embryo (A) that there are quantitative differences between the paraventricular derivatives in PHy (the principal paraventricular nucleus; subdivided by Puelles L. et al. (2012a) into dorsal, central and ventral parts- DPa, CPa, VPa- which show differences with other markers) and THy (dorsal to unstained SCH and AH subparaventricular nuclei); the Pa area of THy contains less important paraventricular populations, but displays preponderant presence of the subpial supraoptic nucleus cells. Another site where islets of Otp-LacZ reaction are found is the basal pm/prm band, here again of larger size in PHy than in THy. Other Otp-expressing cells lie around the ventromedial nucleus (the VM shell), or are mixed with other neurons at the arcuate nucleus (Arc). The latter formation appears strongly counterstained with anti-NKX2.1 immunoreaction (brown), which extends somewhat into the neighboring terminal dorsomedial nucleus subregion (DM-T) and into the medial mamillary body (MM). The diencephalon shows a well-developed habenular complex (Hab), with the descending retroflex tract in characteristic prosomeric position (rf). Note also considerable adult compression of the periventricular stratum of the alar prethalamus (PTh, PThE), always intercalated between thalamus and hypothalamo-telencephalic structures.