Blastula

Cell fate

Terminal differentiation

Xenopus laevis

\b[Can a specialized donor still supply information for other cell types?] The 1962 https://doi.org/10.1242/dev.10.4.622[The Developmental Capacity of Nuclei taken from Intestinal Epithelium Cells of Feeding Tadpoles by J. B. Gurdon] used mid-intestinal cells of feeding <Xenopus laevis> tadpoles. Donors were recognized by columnar shape, basal <cell nuclei> and a striated absorptive border. Dissociation used Versene solution; this made individual donors accessible. The readout was subsequent development, including normal feeding tadpoles, rather than just division or survival. <The Developmental Capacity of Nuclei taken from Intestinal Epithelium Cells of Feeding Tadpoles by J. B. Gurdon>[Gurdon (1962), Material and Methods and Normal tadpoles; inspected primary text reproduced in the indexed Paperity preview]{ref}

\b[Apparatus and intervention.] A microscope with <ultraviolet> illumination directed light at the surface region containing the unfertilized <ovum>'s <chromosomes>, inactivating the recipient nuclear contribution. Irradiation also softened the surrounding jelly so a glass micropipette could enter. The pipette delivered donor nuclear material into recipient <cytoplasm>. In the technique's validation, fertilizing irradiated eggs produced <haploid> embryos, supporting destruction of the maternal nuclear contribution. This is inactivation, not a diagram of surgically removing an intact <cell nucleus>. <The Egg and the Nucleus: A Battle for Supremacy by J. B. Gurdon>[Gurdon, The Egg and the Nucleus: A Battle for Supremacy, The Technique of Nuclear Transfer in Xenopus; indexed authored Nobel lecture text inspected]{ref}

\Image[/frog-intestinal-nucleus-transfer-controls.png]
{title=<Somatic cell nuclear transfer>: intervention, developmental readout and distinct controls}
{description=Original apparatus-and-inference schematic, not a tracing of an experimental photograph. The <ultraviolet> beam indicates inactivation of recipient nuclear material; the injection pipette supplies a donor <cell nucleus>. Donor nuclear markers test origin; interspersed embryonic-donor transfers test recipient quality. Successful development is a possible outcome, not an asserted success rate. The figure omits exact dimensions, light dose and many technical steps.}

\b[Controls ask different questions.] Donor <cell nuclei> carried a marker absent from recipients; post-<blastula> embryos carried that marker. The marker distinguished diploid donors with one <nucleolus> per <cell nucleus> from the usual two-<nucleolus> recipient background, rather than mistaking one <nucleolus> for proof of a <haploid> state. <The Egg and the Nucleus: A Battle for Supremacy by J. B. Gurdon>[Gurdon, Nobel lecture, The Technique of Nuclear Transfer in Xenopus, p. 233: one-nucleolus diploid marker and its use to establish donor nuclear origin]{ref} Interspersed transfers of <blastula> or later embryonic <cell nuclei> checked variable recipient quality. A positive embryonic-donor control thus tests the preparation, while the marker tests donor origin. Abnormal development remained common. Neither control establishes universal transfer competence. <The Developmental Capacity of Nuclei taken from Intestinal Epithelium Cells of Feeding Tadpoles by J. B. Gurdon>[Gurdon (1962), Material and Methods (nuclear marker), Results (interspersed embryonic controls), and Normal tadpoles (abnormal outcomes); primary text inspected through the indexed preview]{ref}

\b[Inference and limits.] A successful marked donor demonstrates that specialization had not irreversibly removed all information required to build other cell types. Failure is less decisive: transfer damage, recipient condition and incomplete <cellular reprogramming> can also prevent development. The marker identifies nuclear origin; it is not a complete <DNA> sequence comparison. The experiment tests donor nuclear potential in an altered <cytoplasm>, rather than normal donor <cell fate>, a universal capacity of every donor, or development from a mature mammalian <red blood cell>. The Nobel account also describes serial transfers through embryonic intermediates; these must not be silently combined with direct transfers into one success rate. <Mature cells can be reprogrammed to become pluripotent by Nobel Assembly at Karolinska Institutet>[Nobel Assembly, Scientific background, Gurdon's nuclear-transfer experiments and serial transplantation]{ref}


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 Incoming links: Intestinal nucleus transfer experiment