Germ cells in natural and experimental chimeras in mammals

Abstract

A chimera can be defined as an individual composed of cells derived from two or more separate zygotes. The incorporation of the two cell lines into the embryo can occur spontaneously or be produced experimentally. It can take place at various periods of embryogenesis and in various ways. It seems that in mammals three mechanisms can be involved (see Tarkowski 1969 for a detailed discussion and references). Double fertilization combined with immediate cleavage of the oocyte at the first or second meiotic division Both dispermy and immediate cleavage have been described but simultaneous occurrence of both events in one egg has not, as yet, been observed, nor experimentally reproduced.

Cytogenetic observations on XX/XY chimaeras and a reassessment of the evidence for germ cell chimaerism in heterosexual twin cattle and marmosets

“…The observations on 1241 cells are summarized in Their assumption that these were germ cells has been questioned by Tarkowski (1970) Barnes & Kruschov, 1968) and that they could have arrived subsequent to birth. Chimaeras that are presumed to have arisen naturally by vascular exchange in utero between fetuses of different sex have also been recorded in man (Race & Sanger, 1975) and in sheep, goat, horse and pig (Marcum, 1974, review by Ford, 1970;Mittwoch, 1973).…”

The Original Function of MHC Antigens as the General Plasma Membrane Anchorage Site of Organogenesis‐Directing Proteins

“…If the notion is that only MHC identical cells can get together and organize an individual body, it is certainly wrong. Two H-2 different blastocysts can fuse and form one healthy mouse (Tarkowski 1970). There apparently exists no H-2 dependent restriction on embryonic development of the mouse.…”

Sexual Conflict in Nonhuman Primates

“…The potential for male-female conflict over the allocation of parental care has long been appreciated (Dawkins & Carlisle, 1976;Trivers, 1972;Westneat & Sargent, 1996). The extensive care of infants by adult males is one of the most striking features of the Callitrichinae (Fernandez-Duque, di Fiore, & Huck, 2012), and recent research suggests an evolutionary role of sexual conflict via the phenomenon of chimerism-the intermingling of two or more genomic lines in one individual (Tarkowski, 1970).…”