Trk C Receptor Signaling Regulates Cardiac Myocyte Proliferation during Early Heart Development in Vivo

Abstract

Neurotrophin-3 (NT-3) is a member of the neurotrophin family of growth factors, best characterized by its survival- and differentiation-inducing effects on developing neurons bearing the trk C receptor tyrosine kinase. Through analysis of NT-3 and trk C gene-targeted mice we have identified NT-3 as critically regulating cardiac septation, valvulogenesis, and conotruncal formation. Although these defects could reflect cardiac neural crest dysfunction, the expression of NT-3 and trk C by cardiac myocytes prior to neural crest migration prompted analysis of cell-autonomous actions of NT-3 on cardiac myocytes. Retroviral-mediated overexpression of truncated trk C receptor lacking kinase activity was used to inhibit activation of trk C by endogenous NT-3, during early heart development in ovo. During the first week of chicken development, expression of truncated trk C reduced myocyte clone size by more than 60% of control clones. Direct mitogenic actions of NT-3 on embryonic cardiac myocytes were demonstrated by analysis of BrdU incorporation or PCNA immunoreactivity in control and truncated trk C-expressing clones. Inhibition of trk C signaling reduced cardiac myocyte proliferation during the first week of development, but had no effect at later times. These studies demonstrate that endogenous NT-3:trk C signaling regulates cardiac myocyte proliferation during cardiac looping and the establishment of ventricular trabeculation but that myocyte proliferation becomes NT-3 independent during the second week of embryogenesis.

Deletion of a kinesin I motor unmasks a mechanism of homeostatic branching control by neurotrophin-3

“…We generated a kinase-dead, GFP-tagged, dominant-negative version of the zebrafish ntrk3a gene orthologous to the gene encoding the TrkC receptor in mammals ( ntrk3adN-GFP ) (Parada et al, 1992). A similar approach was previously shown to efficiently block Ntf3 function in mammalian cells (Tsoulfas et al, 1996; Lin et al, 2000). In zebrafish two TrkC paralogues, ntrk3a and ntrk3b exist, which are both expressed in RGCs (Figure 7A).…”

Transcriptional regulation of Trk family neurotrophin receptors

“…These defects resemble some of the most common congenital heart malformations in humans. It was shown that these cardiac defects were caused by abnormal development of both cardiac neural crest cells and cardiac myocytes [47,49]. Moreover, HF-1b is a transcription factor required for the specification of the cardiac conducting system [113].…”

Constitutive Expression of Preproendothelin in the Cardiac Neural Crest Selectively Promotes Expansion of the Adventitia of the Great Vessels in Vivo

“…Immunoreactivity was detected using 500 g/ml of diaminobenzidine and 0.003% H 2 O 2 in PBS. BrdU detection was performed as previously described using monoclonal-BrdU antiserum, biotinylated anti-mouse IgG, and the Vectastain Elite ABS kit for visualization (Lin et al, 2000). Detection of nuclei was performed by addition of a solution of 1 g/ml DAPI (4Ј,6-diamidino-2-phenylindole; Molecular Probes, Inc., OR) in PBS to sections for 5 min at room temperature, followed by rinsing in PBS.…”