Thrombospondin Type-1 Repeat Domain-Containing Proteins Are Strongly Expressed in the Head Region of <i>Hydra</i>

<div><p>The head region of <i>Hydra</i>, the hypostome, is a key body part for developmental control and the nervous system. We herein examined genes specifically expressed in the head region of <i>Hydra oligactis</i> using suppression subtractive hybridization (SSH) cloning. A total of 1414 subtracted clones were sequenced and found to be derived from at least 540 different genes by BLASTN analyses. Approximately 25% of the subtracted clones had sequences encoding thrombospondin type-1 repeat (TSR) domains, and were derived from 17 genes. We identified 11 TSR domain-containing genes among the top 36 genes that were the most frequently detected in our SSH library. Whole-mount <i>in situ</i> hybridization analyses confirmed that at least 13 out of 17 TSR domain-containing genes were expressed in the hypostome of <i>Hydra oligactis</i>. The prominent expression of TSR domain-containing genes suggests that these genes play significant roles in the hypostome of <i>Hydra oligactis</i>.</p></div