Inductive Interactions Regulating Body Patterning in Planarian, Revealed by Analysis of Expression of Novel Genescarf
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文摘
Subtractive hybridization was used to search for the early difference in gene expression between anteriorly and posteriorly regenerating tissues of the same region of the planarian body. A sequence (namedscarf) specific for posteriorly regenerating tissue was isolated, encoding a soluble C-type lectin consisting of two slightly different carbohydrate-recognition domains. Such an unusual bivalent structure allows attribution of the protein to a novel subfamily of C-type lectins.scarfexpression in intact planarian is rather abundant and follows a characteristic pattern not linked to any known morphological structure. We performed a series of experiments usingscarfas a molecular marker. Its expression was monitored during different types of regeneration by whole-mountin situhybridization and reverse-transcription polymerase chain reaction. The obtained data suggest thatscarfexpression is positively regulated by anterior tissues closely adjacent to thescarf-expressing region, so that their surgical removal results in rapidscarfswitch-off. In turn, tissues expressingscarfseem to inhibit its activation anteriorly. This indicates that at least some of the body patterning events in planarians are based on a system of reciprocal inductive interactions rather than on a global morphogen gradient.