The outflow tract of the heart in fishes: anatomy, genes and evolution

Abstract

A large number of congenital heart defects associated with mortality in humans are those that affect the cardiac outflow tract, and this provides a strong imperative to understand its development during embryogenesis. While there is wide phylogenetic variation in adult vertebrate heart morphology, recent work has demonstrated evolutionary conservation in the early processes of cardiogenesis, including that of the outflow tract. This, along with the utility and high reproductive potential of fish species such as Danio rerio, Oryzias latipes etc., suggests that fishes may provide ideal comparative biological models to facilitate a better understanding of this poorly understood region of the heart. In this review, the authors present the current understanding of both phylogeny and ontogeny of the cardiac outflow tract in fishes and examine how new molecular studies are informing the phylogenetic relationships and evolutionary trajectories that have been proposed. The authors also attempt to address some of the issues of nomenclature that confuse this area of research.

Zebrafish cardiac development requires a conserved secondary heart field

“…Additionally, the loss of Hedgehog signaling has been shown to reduce the size of the heart fields in the zebrafish blastula (Thomas et al, 2008). Given the lack of secondary heart field structures in the zebrafish mutants that we examined, our data support the preliminary investigations of Grimes and Kirby (Grimes and Kirby, 2009) and indicate that the role of these genes in arterial pole development is conserved in teleosts.…”

“…The arterial pole of the zebrafish includes the most cranial myocardium of the ventricle and the large smooth muscle bulbus arteriosus that connects to the ventral aorta (Grimes and Kirby, 2009). The bulbus arteriosus is thought to protect the gills from high blood pressure arising at the ventricle and to prevent backflow (Albrecht et al, 2003;Santer, 1985).…”

KCTD10 is critical for heart and blood vessel development of zebrafish

“…In the mean time, the vmhc signal was also more confined to the abnormal ventricle in the KCTD10-MO-injected embryos (Fig. 7A,B), revealing the defects in cardiac ventricle and outflow tract [17,18]. Furthermore, the expression of cmlc2 showed clearly that in the KCTD10 morphants, both the atrium and the ventricle were hypogenetic as a linear tube (Fig.…”

The Teleost Heart: A Morphological Approach

“…In fact, the overall picture that emerges from the different studies is that the OFT of all primitive fi sh abides to the same general rule. Like primitive fi sh (Parsons 1930 ;Icardo 2006 ;Grimes and Kirby 2009 ) , ancient teleosts show a conus and a bulbus. In all genera studied (Albula, Pterothrissus, Megalops, Elops, Tarpon), the heart shows a muscular conus arteriosus (Parsons 1930 ;Santer 1985 ;Satchell 1991 ) .…”

“…In most primitive fi sh, the OFT is formed by two segments: a proximal, muscular, conus arteriosus, and a distal, arterial-like, bulbus arteriosus (Icardo et al 2002(Icardo et al , 2005aDurán et al 2008 ;Grimes and Kirby 2009 ) . The anatomical composition of the OFT in several other ancient fi sh, like hag fi shes and lampreys, is unclear, but most uncertainties appear to derive from partial observations (Parsons 1930 ;Yamauchi 1980 ) .…”