Hypothesis: Somatic stem cells can acquire germline‑like immortality by undergoing a programmed bottleneck that couples telomerase activation with asymmetric mitochondrial segregation and selective mitophagy. If such a bottleneck is imposed, somatic lineages will show reduced telomere attrition, lower mitochondrial DNA mutation load, and delayed onset of senescence markers compared with controls. Conversely, failure to observe these improvements would falsify the idea that germline‑grade quality control is sufficient to confer somatic longevity.

The germline maintains its integrity across generations not through superior repair but through relentless selection at each reproductive bottleneck: high TERT activity preserves telomeres, a severe mtDNA bottleneck purges deleterious heteroplasmy, and asymmetric division partitions damaged mitochondria into the apoptotic daughter cell[1][3][4]. Somatic cells lack this coordinated pressure, relying instead on diluted repair pathways that eventually succumb to the Hayflick limit[2]. Yet the germline state is plastic—somatic cells can be reprogrammed to a germline‑like phenotype in vitro[1]—indicating that its maintenance toolkit is inducible.

We propose to recapitulate the germline bottleneck in adult somatic stem cells by three coordinated interventions: (1) inducible expression of germline regulators Blimp1 and Prdm14 to trigger epigenetic reprogramming[1], (2) transient TERT overexpression to restore telomerase activity to germline levels[3], and (3) pharmacologic activation of Drp1 to promote mitochondrial fission, thereby enabling asymmetric segregation of organelles[4]. Intestinal crypt stem cells of mice will serve as the test tract because they undergo rapid turnover and display clear senescence readouts. Lineage tracing will track the fate of daughter cells; we predict that the mitochondrion‑enriched daughter will undergo apoptosis, mirroring germline purifying selection, while the other daughter retains a rejuvenated organelle pool.

Readouts will include telomere length quantification by qFISH, mtDNA heteroplasmy depth‑sequencing to assess mutation load, and senescence markers (p16^INK4a, γH2AX, SA‑β‑gal). A successful outcome—significant telomere stabilization, reduction of pathogenic mtDNA variants, and delayed senescence—would support the hypothesis that imposing germline‑grade selection bottlenecks can extend somatic tissue function. Lack of any measurable improvement despite verified induction of the germline program would falsify the claim that such bottlenecks alone confer longevity, indicating that additional germline‑specific constraints (e.g., cytoplasmic niche signals or meiotic recombination) are indispensable.