SOMATIC DIVERSIFICATION OF THE SpTRANSFORMER GENES; A SEA URCHIN IMMUNE GENE FAMILY
Matan Ore, George Washington University
Matan Oren1, Benyamin Rosental2, Teresa Hawley3, Gi-Young Kim4, Jacob Agronin1, Caroline Reinolds1, Megan A. Barela Hudgell1, L. Courtney Smith1
1. Department of Biological Sciences, The George Washington University
2. Institute of Stem Cell Biology and Regenerative Medicine, Stanford University
3. National Cancer Institute, NIH
4. Department of Marine Life Sciences, Jeju National University
Vertebrates depend on adaptive immunity for combating pathogens. A key feature of this system is the ability to diversify certain immune receptor genes (i.e. TCRs, Igs and VLRs) by recombination or copy choice plus hypermutation processes that take place in the soma of the organism. To date, there is very little evidence for similar somatic immune gene diversification in invertebrates. We report that a key immune effector gene family of the purple sea urchin, the SpTransformer (formerly Sp185/333) gene family, diversifies somatically in single immune cells of the same genotype by means of gene deletion, duplication and single point mutations. Gene amplicons in single cells can be different within individual animals relative to amplicons in sperm cells. We also show that all sequences of gene amplicons derived from single cells have full length open reading frames suggesting that the somatic diversification of the family does not generate pseudogenes and therefore may be regulated. Based on the genomic characterization of the family in single cells, two possible mechanisms may be involved in the gene diversification process. First, there may be a mechanism that is based on the positions of the short tandem
repeats (microsatellites) within the gene clusters, and/or second, there may be a vertebrate-like recombination mechanism based on the expression of the sea urchin RAG-like genes.