Orthopedia Homeodomain Protein Is Essential for Diencephalic Dopaminergic Neuron Development

Abstract

Neurons that produce dopamine as a neurotransmitter constitute a heterogeneous group involved in the control of various behaviors and physiology. In mammals, dopaminergic neurons are found in distinct clusters mainly located in the ventral midbrain and the caudal forebrain [1]. Although much is known about midbrain dopaminergic neurons, development of diencephalic dopaminergic neurons is poorly understood. Here we demonstrate that Orthopedia (Otp) homeodomain protein is essential for the development of specific subsets of diencephalic dopaminergic neurons. Zebrafish embryos lacking Otp activity are devoid of dopaminergic neurons in the hypothalamus and the posterior tuberculum. Similarly, Otp-/- mouse [2, 3] embryos lack diencephalic dopaminergic neurons of the A11 group, which constitutes the diencephalospinal dopaminergic system. In both systems, Otp is expressed in the affected dopaminergic neurons as well as in potential precursor populations, and it might contribute to dopaminergic cell specification and differentiation. In fish, overexpression of Otp can induce ectopic tyrosine hydroxylase and dopamine transporter expression, indicating that Otp can specify aspects of dopaminergic identity. Thus, Otp is one of the few known transcription factors that can determine aspects of the dopaminergic phenotype and the first known factor to control the development of the diencephalospinal dopaminergic system.

Homeodomain Protein Otp and Activity-Dependent Splicing Modulate Neuronal Adaptation to Stress

“…The homeodomain-containing protein Orthopedia (Otp) is involved in the embryonic development of a distinct subset of hypothalamic neurons (Acampora et al, 1999; Blechman et al, 2007; Ryu et al, 2007; Wang and Lufkin, 2000). However, Otp expression is maintained in the mature hypothalamus of mouse (Bardet et al, 2008) and zebrafish (Blechman et al, 2007; Ryu et al, 2007).…”

“…However, Otp expression is maintained in the mature hypothalamus of mouse (Bardet et al, 2008) and zebrafish (Blechman et al, 2007; Ryu et al, 2007). A prominent area expressing Otp in CRH-containing neurons is the PVN in mouse as well as the equivalent PO in fish (Figure 1A; see also Figures S1, S2A, and S2B available online).…”

Hematopoietic defects in rps29 mutant zebrafish depend upon p53 activation

“…Genes involved in hematopoiesis, including bcl11a and Notch , were decreased in homozygous mutants but not in heterozygous embryos (data not shown). However, orthopedia protein a ( otpa ), a homeobox containing gene expressed in the brain by 24 hpf[31], was affected in both heterozygous and homozygous mutants. Otpa levels were substantially decreased in the homozygous mutant embryo, but ISH analysis revealed that over one-third of heterozygous embryos had an intermediate phenotype (9 embryos out of 24, Fisher's exact p=0.0013) (Figure 2D).…”

“…Although we could not separate wildtype and heterozygous embryos for the microarray, we could still identify dosage specific defects by whole mount ISH. Orthopedia protein a ( otpa ) is a homeobox containing gene expressed in the brain and important for neuron development[31], and the levels of otpa depend on rps29 levels. The existence of dose-dependent genes with respect to a ribosomal protein suggests a dosage sensitivity model.…”

The Severity of Acute Stress Is Represented by Increased Synchronous Activity and Recruitment of Hypothalamic CRH Neurons

“…p5E-otpa3kb-hsp was created by PCR amplifying ϳ3 kb of the regulatory region of the transcription factor orthopedia a (otpa; Ryu et al, 2007) from genomic DNA and 1.5 kb of the hsp70-4 basal promoter (Halloran et al, 2000), and subcloning both fragments into p5E-MCS. To create the pME-GCaMP3.0 plasmid, full-length GCaMP3.0 (Tian et al, 2009) was PCR amplified from the GCaMP3.0 plasmid (catalog #22692, Addgene) and subcloned into the pME-MCS.…”