Extracellular-matrix gene expression during mouse submandibular gland development

Early morphogenesis of mouse submandibular glands begins on late day 11 of fetal development when the epithelium begins to bud from the surrounding mandibular mesenchyme. Using total RNA collected from fetal BALB/c submandibular glands, steady-state levels of mRNA expression for extracellular matrix molecules were measured using quantitative competitive reverse transcription-polymerase chain reaction (RT-PCR). By comparing the PCR amplification products of both the cellular mRNA and a synthetic template, pMATRIX, if was possible to measure the direct expression of collagens alpha 2(I), alpha 1(III), alpha 1(IV), fibronectin, laminin B-2, elastin and lysyi oxidase genes. There was an observed trend for an increasing concentration of collagen alpha 2(I), collagen alpha 1(III) and lysyl oxidase mRNA molecules per cell on day 16 of development. The relative abundance of elastin mRNA was detectable only on day 16. Fibronectin and laminin B-2 were more constitutively present but had their highest copy number per cell on day 16. The presence of extracellular-matrix protein was confirmed by immunohistochemistry using day-16 fetal glands and adult glands. With the construction of the pMA-TRIX supertemplate and the advent of quantitative, competitive RT-PCR technology, it has been possible to measure small changes in the steady-state concentrations for extracellular-matrix mRNA during salivary gland development. (C) 1997 Elsevier Science Ltd.