Cell Biology

Not So Identical Twins

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Science  27 Jun 2008:
Vol. 320, Issue 5884, pp. 1697
DOI: 10.1126/science.320.5884.1697a

During mitosis, somatic cells divide into two apparently identical daughter cells—but are they really the same? The production of nonidentical daughters occurs during differentiation when one daughter enters one developmental lineage while its sister remains a stem cell. Fuentealba et al. see unequal inheritance even in divisions that had been thought to generate identical daughters; proteins destined for degradation, such as ubiquitinylated Smad1 transcription factor and phospho-β-catenin, were asymmetrically partitioned into one daughter. The process by which these proteins are preferentially inherited involves their microtubule-dependent association with peripheral centrosomal proteins, which is maintained through several rounds of division and in a variety of cell types. The unequal partitioning of misfolded and aggregated proteins in so-called aggresomes has already been observed, and this capacity for keeping one daughter free of defunct proteins may help to avoid a wholesale loss of cell populations if the load of such potentially damaging proteins becomes too great. — SMH

Proc. Natl. Acad. Sci. U.S.A. 105, 7732 (2008).

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