Expression of TGF-β Superfamily Receptors in Dental Pulp

Abstract

Transforming growth factor-β (TGF-β) superfamily members and their cell-surface receptors may play inductive and/or regulatory roles in tooth development and repair. It will be important to identify the complete set of TGF-β superfamily receptors, to examine their temporal and spatial localization during tooth development, and to elucidate the cascade of molecular events of tooth formation induced by the TGF-β superfamily. In this report, we have cloned the cDNAs encoding potential receptors for TGF-β superfamily members in rat incisor pulp and bovine adult pulp which are regarded as embryonic and adult pulp, respectively. We analyzed poly (A)+ RNA from rat incisor pulp and bovine adult pulp by reverse-transcriptase/polymerase chain-reaction (RT-PCR), using degenerate primers corresponding to the most conserved amino acid sequences in the intracellular serine/threonine kinase of type I or type II receptors. Each amplified cDNA encoding activin receptor-like kinase-1 (ALK-1), ALK-2, ALK-3 (bone morphogenetic protein receptor type IA, BMPR-IA), ALK-4 (Bl), ALK-5, ALK-6 (BMPR-IB), and BMPR-II (BMP type II receptor) was found to be in dental pulp. Northern blot analysis further detected TGF-β type II receptor (TβR-II) mRNA transcript in addition to the above-identified receptors. These results provide the first evidence of multiple type I and type II receptors for TGF-βs, activins, and BMPs expressed in embryonic and adult pulp, implicating diverse function in tooth development and pulp tissue repair.