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Inflammatory processes are implicated in preterm labour (PTL). To identify potential novel markers for PTL, we have used commercial cDNA arrays to generate profiles of differential expression of inflammation-associated genes in gestational membranes with term and PTL. RNA for cDNA probe synthesis was isolated from reflected human amnion and choriodecidua membranes delivered following Caesarean section at term before the onset of labour (TNL, n = 4), spontaneous labour at term (TSL, n = 4), and PTL with and without chorioamnionitis (PTL(+INF) and PTL(-INF) respectively, n = 4 each). Profiles were displayed relative to TNL and statistical comparisons of TSL versus TNL and PTL(+INF) versus PTL(-INF) were performed. Elevated expression of chemokines macrophage inflammatory protein 1beta(MIP-1beta) and pulmonary and activation-regulated chemokine (PARC) was observed in PTL(+INF) compared to PTL(-INF) amnion and choriodecidua respectively (P = 0.03). Likewise, the cytokines oncostatin-M and pre-B cell enhancing factor (PBEF) were more highly expressed in PTL(+INF) compared with PTL(-INF) and in TSL compared with TNL respectively (P = 0.03). Conversely, inhibin A, tissue inhibitors of matrix metalloproteinase (TIMP)-3 and TIMP-4 were all significantly elevated in PTL(-INF) compared with PTL(+INF) (P = 0.03). Furthermore, differential expression patterns of classes of genes, grouped according to function (e.g. chemokines), were noted. The cDNA array approach holds promise for identification of new candidate markers or combinations thereof for prediction or diagnosis of PTL, as well as for increasing our understanding of the particular aetiologies involved.

In this study, we have characterized the cDNA clone SQ37 that was isolated previously from a rabbit squamous cell library. The gene encodes a 14-kDa protein that appears to function as a component ofthe cross-linked envelope in squamous differentiating cells. The protein, which has been named cornifin, has a high content of proline (31%), glutamine (20%), and cysteine (11%) and contains 13 repeats of an octapeptide (consensus sequence, EPCQPKVP) at its C terminus. SQ37 mRNA and protein are induced during squamous differentiation of rabbit tracheal (RbTE) cells and human epidermal keratinocytes. This induction is repressed by retinoids. Immunohistochemical studies reveal SQ37 immunoreactivity in fragmented cross-linked envelopes from squamousdifferentiated RbTE cells and in the suprabasal layers of the epidermis. In situ hybridization analysis showed that the presence of SQ37 mRNA is restricted to the suprabasal layers.Treatment of RbTE cells with a Ca2W ionophore induces cross-linking of the SQ37 protein into higher molecular weight complexes. This cross-linking reaction appears to be mediated by transglutaminase type I. Our observations suggest that the protein encoded by SQ37 participates in the assembly of the cross-linked envelope.Epithelial cells from many different tissues are able to undergo squamous differentiation. In the tracheobronchial epithelium this differentiation occurs during vitamin A deficiency and after toxic or mechanical injury (1, 2). In other tissues, including skin, squamous differentiation constitutes the normal pathway of differentiation (3). The existence of histologically distinct layers in squamous epithelia is indicative of a multistage process of differentiation (3,4). This view is supported by observations that each of these stages can be defined by the expression of specific biochemical and molecular markers (5-8). The formation of the cross-linked envelope is a characteristic feature during later stages of differentiation (9-11). The highly insoluble cross-linked envelope consists of a layer of covalently linked protein assembled just beneath the plasma membrane. Transglutaminases catalyze the formation of E-(y-glutamyl)lysine isopeptide bonds between cross-linked envelope precursors (11-15). Several proteins have been implicated in the formation of the cross-linked envelope, including involucrin and loricrin, which have been studied in detail (11,(16)(17)(18)(19)(20)(21)(22). The genes for these proteins have been cloned and sequenced (22)(23)(24).Previously, this laboratory has reported (25) the isolation of several cDNA clones, including SQ37, that encode mRNAs abundantly expressed in differentiating squamous RbTE cells. In the present study, the DNA and protein sequences of cDNA clone SQ37 were analyzed. The predicted coding region of SQ37 shows high homology with that of the human gene for the small proline-rich protein 1 (spr-1) (26,27). However, no function has been described for either gene product. Evidence presented in this study is consistent with the hypothe...