Smith Charles E, Nanci Antonio, Moffatt Pierre
Laboratory for the Study of Calcified Tissues and Biomaterials, Faculté de Médecine Dentaire, Université de Montréal, Montréal, Québec, Canada.
Eur J Oral Sci. 2006 May;114 Suppl 1:147-53; discussion 164-5, 380-1. doi: 10.1111/j.1600-0722.2006.00273.x.
During screening of a rat incisor enamel organ cDNA library by signal peptide trap technology, we identified a DNA fragment matching a predicted translation sequence for rat carbonic anhydrase 6 (CA6). This result was unexpected because CA6, to date, has been associated primarily with secretions from glandular tissues. To further characterize this observation, reverse transcription-polymerase chain reaction (RT-PCR) amplifications were carried out on total RNA extracted from freeze-dried secretory and maturation-stage rat incisor enamel organs. A cDNA fragment of the expected size was detected in control samples from rat salivary glands as well as within maturation-stage enamel organ samples. This CA6 RT-PCR fragment was further cloned and sequenced and found to match the nucleotide sequence 770-1079 from clone XM_216584 of GenBank. Northern blot analyses with the rat CA6 cDNA fragment confirmed its expression relative to maturation-stage enamel organ samples. It is at present unclear whether the CA6 expressed by enamel organ cells is secreted into the enamel layer or into the intercellular spaces of the enamel organ itself to assist in neutralizing excess protons arising from the growth of apatite crystals during the maturation stage of amelogenesis.
在用信号肽捕获技术筛选大鼠切牙釉质器官cDNA文库的过程中,我们鉴定出一个与大鼠碳酸酐酶6(CA6)预测翻译序列相匹配的DNA片段。这一结果出人意料,因为迄今为止,CA6主要与腺组织的分泌物相关。为了进一步研究这一发现,我们对从冻干的分泌期和成熟期大鼠切牙釉质器官中提取的总RNA进行了逆转录聚合酶链反应(RT-PCR)扩增。在大鼠唾液腺的对照样本以及成熟期釉质器官样本中都检测到了预期大小的cDNA片段。这个CA6 RT-PCR片段被进一步克隆和测序,结果发现它与GenBank中克隆XM_216584的核苷酸序列770 - 1079相匹配。用大鼠CA6 cDNA片段进行的Northern印迹分析证实了其在成熟期釉质器官样本中的表达。目前尚不清楚釉质器官细胞表达的CA6是分泌到釉质层中,还是分泌到釉质器官自身的细胞间隙中,以协助中和在釉质形成成熟阶段磷灰石晶体生长过程中产生的过量质子。