Cloning of Numb and its vital role in the development of <i>Exopalaemon carinicauda</i> (Holthuis, 1950) (Decapoda: Caridea: Palaemonidae)

Abstract Numb is a conserved protein that modulates various signaling pathways to regulate asymmetric cell division and determine cell fate. To investigate the role of Numb in the development of Exopalaemon carinicauda (Holthuis, 1950), Numb cDNA was cloned from E. carinicauda using RACE (rapid-amplification of cDNA ends), expression characterization was performed using qRT-PCR, functional analysis was performed using RNA interference (RNAi) and by histological sectioning. The results revealed that the Numb cDNA of E. carinicauda (Ec-numb) is 2375 bp, encoding a 627 amino acid protein containing one Asp-Pro-Phe (DPF)-Asn-Pro-Phe (NPF) motif, one phosphotyrosine-binding (PTB) domain and one Numb family (Numb-F) domain. Ec-Numb had the highest identity with Procambarus clarkii (Girard, 1852) (78.99%). The highest expression of Ec-numb was detected at the mysis stage during larval development and in the ovaries among the different tissues. After Numb was knocked down by RNAi, the expression of notch, snob1, jagged, delta, wnt, mih, chh, vasa and vg increased significantly (P &amp;lt; 0.05), and gih decreased significantly (P &amp;lt; 0.05). After successive RNAi, the gonadosomatic index (GSI) of the RNAi group was significantly greater than that of the control group (P &amp;lt; 0.05). The histological sections revealed that the ovaries in the RNAi group had developed to the G3 stage, whereas those in the control group were still at the G2 stage. These results indicated that Numb potentially played a negative regulatory role in the development of E. carinicauda by regulating the Notch/Wnt signaling pathway, providing new insight into the molecular mechanisms regulating reproductive development in decapod crustaceans.