近年來研究發現在節肢動物中Down syndrome cell adhesion molecules (Dscam)分子，具備有專一性辨認抗原之特性，因而被識為參與類適應性免疫機制的一員 (alternative adaptive immunity)。而節肢動物之Dscam分子能夠具有此專一性辨認抗原的能力，是由於此基因能夠透過未成熟RNA之選擇性剪接機制，產生出變異性極高的蛋白質，進而達到此免疫能力。而參與選擇性剪接機制的調控因子，主要可分為剪接活化因子及剪接抑制因子，目前研究最多的剪接活化因子為絲氨酸/精氨酸蛋白質家族 (Serine/arginine - rich proteins family)。先前研究認為絲氨酸/精氨酸蛋白家族的B52蛋白，可能參與活化果蠅Dscam的選擇性剪接，因此本研究進一步探討B52蛋白是否能參與白蝦Dscam之選擇性剪接機制。首先本研究已鑑定出第一個白蝦 (Litopenaeus vannamei) B52基因 (LvB52)。接著我們將白蝦活體內LvB52基因沈默化，來探討LvB52在白蝦Dscam的選擇性剪接之角色，結果顯示當LvB52基因弱化後，LvDscam Ig2、Ig3及Ig7 之 isoform多樣性呈現降低趨勢。另外也發現在LvDscam細胞質尾區的第三元素區 (element 3) 的外顯子跳躍機制 (exon skipping) 有顯著性增加。此外本研究發現，當白點症病毒感染白蝦後24小時，LvDscam以及LvB52基因表現量皆有上升的現象。而若將LvB52基因弱化後再感染白點症病毒24小時，則發現此時LvDscam的基因表現量會受到抑制，另外也發現LvDscam主要與病原體結合的變異區域Ig3 之多樣性也有顯著減少現象。由以上結果可推論出在健康及受到白點症病毒感染的白蝦中，LvB52的確皆能調節LvDscam的選擇性剪接機制。

Over the last decade, arthropod Down syndrome cell adhesion molecules (Dscam) have been known to involve in the mechanism of alternative adaptive immunity. Through the alternative splicing, it can be generated tens of thousands of isoforms to specific recognize pathogens. Some alternative splicing factors have been reported to regulate the alternative splicing of Dscam, including the splicing activators and repressors. In this study, we identified the serine/arginine - rich protein B52, an alternative splicing activator, which is involved in the alternative splicing of Litopenaeus vannamei Dscam (LvDscam). We first characterized the B52 gene from L. vannamei, named LvB52. Subsequently, in vivo dsRNA silencing of LvB52 induced element 3 exon exclusion in the LvDscam cytoplasmic tail, but no abnormal exclusions in the Ig2-Ig3 and Ig7 regions or the transmembrane region. In addition, LvB52 silencing was associated with a decrease in the complexity of LvDscam Ig2, Ig3 and Ig7 regions. After white spot syndrome virus (WSSV) infection, a parallel increase in the expression of total LvDscam, tail-less LvDscam, membrane-bound LvDscam and LvB52 was observed after 24 hpi. Besides, the LvDscam expression and the exon complexity of its Ig3 region were decreased obviously in LvB52-silenced shrimp after 24h post WSSV infection. Taken together, our data suggest that LvB52 acts as a splicing activator that regulates the LvDscam AS events in both healthy and WSSV infection conditions.

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