EXPRESSION OF TGF-BETA SUPERFAMILY RECEPTORS IN DENTAL-PULP

Transforming growth factor-beta (TGF-beta) superfamily members and the ir cell-surface receptors may play inductive and/or regulatory roles i n tooth development and repair. It will be important to identify the c omplete set of TGF-beta superfamily receptors, to examine their tempor al and spatial localization during tooth development, and to elucidate the cascade of molecular events of tooth formation induced by the TGF -beta superfamily. In this report, we have cloned the cDNAs encoding p otential receptors for TGF-beta superfamily members in rat incisor pul p 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 t ype I or type II receptors. Each amplified cDNA encoding activin recep torlike kinase-l (ALK-1), ALK-2, ALK-3 (bone morphogenetic protein rec eptor type IA, BMPR-IA), ALK-4 (B1), ALK-5, ALK-6 (BMPR-IB), and BMPR- II (BMP type II receptor) was found to be in dental pulp. Northern blo t analysis further detected TGF-beta type II receptor (T beta R-II) mR NA transcript in addition to the above-identified receptors. These res ults provide the first evidence of multiple type I and type II recepto rs for TGF-beta s, activins, and BMPs expressed in embryonic and adult pulp, implicating diverse function in tooth development and pulp tiss ue repair.