Figure 1.

Representation of the genomic organization and splicing patterns of Ighμ in teleosts and catfish. Ighμ generally encodes a VH domain, four constant (Cμ₁ to Cμ₄) domains and two transmembrane domains. For full-length cDNA Ighμ transcripts in bighead catfish, North African catfish and their hybrid catfish, three major molecular techniques were performed (A). Patterns of PCR amplification products, 5’ RACE PCR (B), internal constant domain (C), and 3’ RACE PCR (D) of Ighμ of bighead catfish, North African catfish and their hybrid catfish. A single gene copy (NCBI accession no. MZ559374) and six different Ighμ transcripts were identified in bighead catfish, and five and one were expressed as membrane (NCBI accession nos. MN934742, MN934743, MN934744, MN934745 and MN934746) and secreted forms (NCBI accession no. MN934747), respectively. Moreover, two membrane forms of Ighμ transcripts had novel splicing patterns in teleosts and vertebrates (highlighted in yellow) (NCBI accession nos. MN934745 and MN934746) (E). A single gene copy (NCBI accession no. MZ559375) and three different Ighμ transcripts were identified in North African catfish; two and one were expressed as membrane (NCBI accession no. MN934748 and MN934749) and secreted forms (NCBI accession no. MN934750), respectively (F). Two gene copies (NCBI accession nos. MZ559376 and MZ559377) and two Ighμ transcripts were identified in the hybrid catfish (NCBI accession nos. MN934751 and MN934752) (G). Comparisons of cytogenetic localization of Ighμ gene loci in bighead catfish (H), North African catfish (I) and their hybrid catfish (J). All nucleotide sequences are illustrated in supplementary files and the NCBI database corresponding to the provided NCBI accession numbers.