Species differ in tooth size, spacing and shape in coordinated style. We focus on 3 closely connected Lake Malawi cichlids with option dental phe notypes, Cynotilapia afra, a uni cuspid species with two tooth rows of massive, widely spaced teeth, Metriaclima zebra, a bicuspid and tricuspid species with five or six tooth rows of intermedi ately sized and spaced teeth, and Labeotropheus fuelleborni, a uniformly tricuspid species with ten or extra tooth rows of little, tightly packed teeth. Previously, we’ve used these species to determine the chromosomal basis of divergent tooth shapes among spe cies. Here we address a unique query, we ask how conserved gene networks are deployed to influence the diversity within the size, number, spacing inside rows and quantity of rows of teeth.
Results and Discussion Variation in developmental gene networks prefigures variations in adult cichlid dentitions We cloned cichlid orthologues of genes expected during oral epithelial organization and tooth germ initiation as well as mesenchymal markers involved in recip rocal signalling to the epithelium. Teleost tooth development read this post here has been effectively characterized in the zebrafish and thus our nomenclature for the early stages of tooth development will adhere to that model. Two stages of early odontogenesis are relevant, the thickened epithelium stage and also the bell shaped epithelium stage. Devel oping teeth beyond this point are going to be referred to as tooth germs, spanning the progression on the tooth from a bell shaped unit to many stages of functional maturity, char acterized by cytodifferentiation.
The transcription aspect pitx2, described as a putative odontogenic commissioning gene, has a broad expression pattern that encompasses each the building tooth unit along with the inter tooth area, marking the extent with the dental competent oral epithelium, like regions of future tooth rows. pitx2 selleck is among the earliest dental epithelial markers with expression within the thickened dental epi thelium and each the inner dental epithelium and outer dental epithelium of the maturing tooth. Interestingly, the early pattern of pitx2 expression differs across the three species prior to and for the duration of morphogenesis with the initially tooth, and reflects the future organization of those distinct dentitions. L. fuelleborni shows the greatest region of dental com petence, consistent using the later elaboration of teeth and tooth rows.
Future tooth rows also show expression of pitx2, labelling the lingual progression of your subsequent OB. Equivalent to research in other fishes, we found that fgf8 expression is just not connected with initiating tooth germs in Malawi cichlids. pax9, on the list of earliest mesenchymal markers of odon togenesis in the mouse, is either absent from or weakly expressed within the dentitions of zebrafish and Mexican tetra.