Genetic Chimerism of Marmosets (Callithrix kuhlii) C.N. Ross1, G. Ortí1, and J.A. French2 1University of Nebraska at Lincoln, Department of Biology, Lincoln, NE 2University of Nebraska at Omaha, Department of Psychology, Omaha, NE • Methods • University of Nebraska at Omaha has maintained a small colony of C. kuhlii since 1990. • Forty twin sets were assayed using four published microsatellite markers (CJ1, CJ13, CJ14, CJ6, Neivergelt et al, 1998. Mol Ecol7:1431-1439). • Tissues included liver, heart, kidney, gonad, muscle, skin, hair, fecal, spleen, and blood. • Fluorescent-labeled PCR products were analyzed using GeneScan on an ABI 310 genetic analyzer. • Species specific microsatellite primers are being developed using Lunt et al (1999. Mol Ecol8: 891-894) protocol for genomic enriched motifs. • Introduction • Marmosets and tamarins typically give birth to fraternal twins, which on average weigh 16-20% of the female's body mass. The large reproductive burden on the female has been suggested as the cause for the development and maintenance of a communal care social system. The actual paternity of the offspring has been difficult to determine by behavioral measures, making this system a great candidate for microsatellite paternity exclusion. A complicating factor is the fact that early in development the fraternal twins develop placental bone -marrow anastomoses that allow blood flow between the twins (photo below). Initial karyotyping studies revealed XY chromosomes in the liver of a female whose twin was a male, thus making her a chimeric individual. • Goals of this study: • To develop microsatellite markers specific for C. kuhlii (Weid’s Black Tufted-Ear Marmoset). • To document the extent and distribution of chimerism. • Predictions: • Tissues derived from bone marrow stem cells (liver, blood, and spleen) will be chimeric. • Non-bone marrow derived tissues such as hair and muscle will not be chimeric, genetic information should exclusively represent native genotypes. • Discussion • Preliminary results suggest that tissues from marmosets are chimeric. The existence of three alleles for a single locus suggests strong evidence for the presence of chimerism not only in bone marrow derived cells (liver and spleen), but also in a variety of other tissues including gonadal tissues. • These findings may have interesting implications for other fields of research: • Determination of individuality for paternity exclusion and conservation strategies. • Predictions for the evolutionary transfer of genetic information. • Predictions for paternal investment and paternal care. • Predictions for cooperative breeding efforts. Preliminary Results GeneScan results for locus CJ1 for one individual. Allele size is reported as the number of base pairs (red peaks are size standard, blue shaded peaks are alleles). Liver and spleen tissues for this individual appear to be chimeric, exhibiting three peaks for one locus; while lung, muscle, and gonad tissue only have two peaks. Liver Spleen Most Intriguing: Fraternal twins may be fertilized by sperm from two males. Therefore, chimerism may allow an individual to express genes from TWO fathers. Lung Muscle Gonad Genotypes of an individual differ across tissues. • Future Research • Continue development of new species specific • microsatellite loci. • Assess active germ line cells (i.e. sperm). • Evaluate paternity exclusion in this captive colony. However, chimerism is NOT limited to bone marrow tissues. Acknowledgements: We would like to thank the National Science Foundation, UNL Special Funds, UNL Layman's Grant, UNL Initiative for Ecological and Evolutionary Analysis, Sigma Xi and American Society of Primatologists for grants supporting this research. We would also like to thank Justin Meeker, Alicia Startzer, Sara Brant, Jeffrey Fite, Erin Kinnally, Mike Bessert and Annie Paradis for help in sample collection and analysis. Heart Gonad Genescan results for additional microsatellite loci (CJ13, CJ14) reveal that three alleles may be found in a multitude of tissues including gonad and heart tissue.