Characterization of the hypothalamus of Xenopus laevis during development. I. The alar regions

Abstract

The patterns of expression of a set of conserved developmental regulatory transcription factors and neuronal markers were analyzed in the alar hypothalamus of Xenopus laevis throughout development. Combined immunohistochemical and in situ hybridization techniques were used for the identification of subdivisions and their boundaries. The alar hypothalamus was located rostral to the diencephalon in the secondary prosencephalon and represents the rostral continuation of the alar territories of the diencephalon and brainstem, according to the prosomeric model. It is composed of the supraoptoparaventricular (dorsal) and the suprachiasmatic (ventral) regions, and limits dorsally with the preoptic region, caudally with the prethalamic eminence and the prethalamus, and ventrally with the basal hypothalamus. The supraoptoparaventricular area is defined by the orthopedia (Otp) expression and is subdivided into rostral and caudal portions, on the basis of the Nkx2.2 expression only in the rostral portion. This region is the source of many neuroendocrine cells, primarily located in the rostral subdivision. The suprachiasmatic region is characterized by Dll4/Isl1 expression, and was also subdivided into rostral and caudal portions, based on the expression of Nkx2.1/Nkx2.2 and Lhx1/7 exclusively in the rostral portion. Both alar regions are mainly connected with subpallial areas strongly implicated in the limbic system and show robust intrahypothalamic connections. Caudally, both regions project to brainstem centers and spinal cord. All these data support that in terms of topology, molecular specification, and connectivity the subdivisions of the anuran alar hypothalamus possess many features shared with their counterparts in amniotes, likely controlling similar reflexes, responses, and behaviors.

Expression of a novel serine/threonine kinase gene, Ulk4, in neural progenitors during Xenopus laevis forebrain development

“…For example xUlk4 expression is found in the PO, which is involved in the control of reproductive behavior and reproduction both in amniotes and anamniotes (Kelley and Pfaff, 1976;Hodos, 1996, 2005;Boulant, 1998;Will et al, 2014;Yaeger et al, 2014). In addition there is high xUlk4 expression detected in the Xenopus hypothalamic territory, which presents a homologous regionalization pattern to the one described in mammals, as has been recently reported by an exhaustive study based on morphogenetic, neurochemical and hodological patterns (AH: supraoptoparaventricular and SCs; BH: tuberal and mammillary regions; Domı´nguez et al, 2013Domı´nguez et al, , 2014. We have observed xUlk4 expressing cells in the supraoptoparaventricular and SCs, which are closely related to the neuroendocrine system, containing neuroendocrine cells involved in the control and regulation of different physiological functions such as social and reproductive behavior, stress response and sleep among others (for a review see Markakis, 2002;Miller and Takahashi, 2013).…”

“…To this aim, we have here studied the expression of Ulk4 during the development of the nervous system in the amphibian Xenopus laevis. In the last years, numerous comparative studies of diverse transcription factor expression patterns in the embryonic brain have strongly supported the idea of a common brain organization pattern across tetrapods (Figdor and Stern, 1993;Rubenstein, 1993, 2003;Pombal and Puelles, 1999;Wullimann and Puelles, 1999;Hauptmann and Gerster, 2000;Puelles et al, 2000;Bachy et al, 2001Bachy et al, , 2002Gonza´lez et al, 2002a,b;Brox et al, 2003Brox et al, , 2004Osorio et al, 2005Osorio et al, , 2006Flames et al, 2007;Abella´n and Medina, 2009;Gonza´lez and Northcutt, 2009;Abella´n et al, 2010;Domı´nguez et al, 2010Domı´nguez et al, , 2011Domı´nguez et al, , 2013Domı´nguez et al, , 2014Moreno et al, 2010Moreno et al, , 2012Moreno and Gonza´lez, 2011;Lo´pez et al, 2012;Lo´pez and Gonza´lez, 2013), highlighting Xenopus as a valid model for the present anatomical study.…”

“…The nomenclature used in the present study is supported by several recent studies that have proposed a new prosencephalic regionalization in anurans based on exhaustive mapping studies (Puelles et al, 1996;Gonza´lez et al, 2002a,b;Brox et al, 2003;Moreno et al, 2004Moreno et al, , 2008aMorona and Gonza´lez, 2008;Domı´nguez et al, 2010Domı´nguez et al, , 2011. In the case of the hypothalamic region, we have followed the recent nomenclature proposed for Xenopus by Domı´nguez and collaborators (Domı´nguez et al, 2013 which is based on tract tracing, immunohistochemistry and gene expression patterns.…”

Conserved localization of Pax6 and Pax7 transcripts in the brain of representatives of sarcopterygian vertebrates during development supports homologous brain regionalization

“…The specificity of the antibodies had previously been tested in most of the species used in this comparative analysis (Ferran et al, 2009; Moreno et al, 2010; Morona et al, 2011; Domínguez et al, 2013, 2014; Joven et al, 2013a,b). Moreover, the immunoblotting conducted with brain extracts of all the species used showed that the Pax6 and Pax7 antibodies labeled a single band at comparable molecular weight across species ( Figure 2 ).…”

“…The mouse anti-Pax6 and anti-Pax7 antibodies developed by Kawakami et al (1997) are the most widely used in anatomical studies, independently of the species studied (Ferran et al, 2008, 2009; Morona et al, 2011; Moreno et al, 2012b; Bandín et al, 2013, 2014; Domínguez et al, 2013, 2014; Joven et al, 2013a,b). In order to develop the antibodies against Pax6 and Pax7, Kawakami et al (1997) first determined the complete nucleotide sequence of the full-length cDNA encoding for Pax6 and Pax7.…”