LongeCityNews Last Updated: 06 February 2026 - 10:46 PM

The degree to which human longevity is inherited is one of a large number of interesting research topics that, while being related to aging, has little to no relevance to the question of how to treat aging as a medical condition. In developing means to repair or resist the cell and tissue damage that causes degenerative aging, the focus must be on the damage, not the differences from individual to individual. How it is that aging progresses somewhat differently from individual to individual will become increasingly irrelevant as therapies to slow and reverse aging emerge.

That said, today's open access paper on the heritability of longevity is quite interesting. The argument put forward by the authors is that previous efforts to quantify the degree to which individual variance in longevity is determined by one's immediate ancestry have produced underestimates because they failed to properly compensate for the effects of premature death resulting from accidents, infectious disease, and the like. If the strategy for assessment used in the paper is employed instead, then human heritability of longevity is higher than past results, and also more in line with the heritability of other physical traits.

At the same time, the big picture on the genetics of aging that has emerged in recent years, with the advent of very large population databases such as the UK Biobank, is that genetics plays only a small role in determining life expectancy. It is far outweighed by lifestyle choice in the vast majority of people. A high heritability but low contribution of genetic variance suggests that heritability largely exists as a result of the cultural transmission of lifestyle choices; parents that take better care of their health tend to have children who take better care of their health, and vice versa.

Heritability of intrinsic human life span is about 50% when confounding factors are addressed

Understanding the heritability of human life span is fundamental to aging research. However, quantifying the genetic contribution to human life span remains challenging. Although specific life span-related alleles have been identified, environmental factors appear to exert a strong effect on life span. Clarifying the heritability of life span could direct research efforts on the genetic determinants of life span and their mechanisms of action.

Previous studies have estimated the heritability of life span in various populations with results ranging from 15 to 33%, with a typical range of 20 to 25%. Recently, studies on large pedigree datasets estimated it at 6 to 16%. These studies contributed to growing skepticism about the role of genetics in aging, casting doubt on the feasibility of identifying genetic determinants of longevity. Current estimates for the heritability of human life span are thus lower than the heritability of life span in crossbred wild mice in laboratory conditions, estimated at 38 to 55%. They are also lower than the heritability of most other human physiological traits, which show a mean heritability of 49%.

Most life-span studies used cohorts born in the 18th and 19th centuries, with appreciable rates of extrinsic mortality. Extrinsic mortality refers to deaths caused by factors originating outside the body, such as accidents, homicides, infectious diseases, and environmental hazards. Another factor that varies between studies is the minimum age at which individuals must be alive to be included, referred to as the cutoff age. To our knowledge, these two factors - extrinsic mortality and cutoff age - have not been systematically investigated for their effect on heritability estimates of life span.

Here, we explored the effects of extrinsic mortality and cutoff age on twin study estimates of heritability. We used model-independent mathematical analysis and simulations of two human mortality models to partition mortality into intrinsic and extrinsic components. We tested our conclusions on data from three different twin studies, including the SATSA (Swedish Adoption/Twin Study of Aging) study, containing data from twins raised apart that have not been previously analyzed for life-span heritability. To test generalizability to non-Scandinavian cohorts, we also analyzed siblings of US centenarians. We found that extrinsic mortality causes systematic underestimates of the heritability of life span and that cutoff age has a mild nonlinear effect on these estimates. When extrinsic mortality is accounted for, estimates of heritability of life span due to intrinsic mortality rise to about 55%, more than doubling previous estimates.

Life Biosciences has announced that its trial of cellular reprogramming aimed at two age-related vision diseases has received a go-ahead from the FDA. We spoke with the company’s CSO to get more details.

Life Biosciences, the biotech company based on Harvard professor David Sinclair’s research into cellular reprogramming, stunned everyone last year by announcing that its clinical trial, the first-ever human trial of a reprogramming technology, will commence in the first quarter of 2026. A few days ago, the company cleared the last major hurdle on its way to this ambitious goal by receiving an Investigational New Drug (IND) clearance from the FDA to test the experimental drug ER-100 against optic neuropathies.

ER-100’s story begins with highly successful experiments in rodents, where Sinclair’s team used their own partial cellular reprogramming recipe to restore vision after a severe optic nerve injury, and then proceeded to a successful trial in non-human primates. This upcoming trial is focused on open-angle glaucoma (OAG) and non-arteritic anterior ischemic optic neuropathy (NAION), which is a “stroke of the eye” that can cause sudden blindness. Both diseases are age-related, with NAION being the most common acute optic neuropathy in adults over fifty.

Life Biosciences uses a proprietary reprogramming cocktail based on three out of four of the original Yamanaka factors: OCT-4, SOX-2, and KLF-4 (OSK). The company believes that this approach solves several problems that plagued early reprogramming research.

“It’s incredibly meaningful to see this science reach clinical testing after more than 30 years of work,” Sinclair said to Lifespan News. “I’m grateful to the many students, collaborators, and partners whose dedication helped bring these ideas from the lab to this milestone. For me personally, it’s deeply rewarding to see this work move into the clinic, with the potential to protect and restore vision for patients and to help unlock a new generation of therapies that target the diseases of aging across tissues.”

As this is the first reprogramming clinical trial, and one of the first longevity therapy clinical trials, many people in this industry view it as a seismic event. “This is a huge milestone for the entire partial reprogramming field, and it aligns with what we’ve seen as well: the FDA has been notably open and forward-thinking in how it engages with this approach,” said Yuri Deigin, CEO of YouthBio, which is developing its own anti-Alzheimer’s reprogramming-based therapy. “It’s also a strong signal for the broader longevity space that regulators are increasingly willing to evaluate therapies that aim to modify upstream epigenetic drivers of aging, rather than only treating downstream symptoms.”

We have long followed Life Biosciences and interviewed both David Sinclair and Life CSO Sharon Rosenzweig-Lipson. Following the FDA clearance announcement, we spoke with Sharon again to get her perspective on the trial timeline, Life Biosciences’ experience of interacting with the FDA, and the company’s future trajectory.

When are you planning to start the actual trial, and when can we expect results?

We’re in the final stages of getting our first site activated. We expect that to happen within a few weeks and to start enrolling patients right after that. By March, we’ll have begun enrolling patients.

And the ETA on results?

Because it’s a gene therapy, we’re going to enroll patient number one, wait 28 days, then enroll patients two and three, wait another 28 days. Then we’ll make decisions about going up and down on the dose. It’s going to take time to get through that, but we hope to have enough information by the end of the year on one or more doses. This will allow us to make decisions about whether we go to Phase 2 and start planning the next stage. We’re as eager as everybody else to move this as quickly as possible.

Usually, partial reprogramming involves pulsing with very carefully calculated doses so that the cells don’t undergo dedifferentiation. I understand that your therapy is “one-shot” – based on a single round of continuous administration.

I want to separate what we call partial reprogramming from what others do, which is transient reprogramming. Sometimes, you see transient reprogramming where you give it one or two days, wait a few more days in animals, then give it one or two more days. That’s often done with all four factors.

That’s not what we’re doing. We’re going to give doxycycline systemically – it’s an inducible system – keeping OSK on for an eight-week period. We have data showing that we can do it not just for two months, but for three months, or even beyond that in mice, demonstrating that we can achieve good reprogramming and good safety with a more continuous expression system.

Do you see at least some shift toward dedifferentiation with more time on the therapy?

We do not. What’s amazing about using OSK is that it’s not causing de-differentiation. It’s resetting the epigenetic code. That code, which made normal hearts, lungs, livers, retinal ganglion cells, gets degraded as we age or with age-related diseases. Our therapy resets that code back to a healthy, youthful state, but not all the way back, not to pluripotency. Cell identity is maintained.

It looks like you cracked one of the hardest problems in partial reprogramming by taking out the M out of the original four-factor Yamanaka cocktail.

Exactly. Taking the M out makes it impossible to go all the way back. You just can’t push the system hard enough.

What can you tell me about your interactions with the FDA? Was there something that pleasantly surprised you?

We met with the FDA almost two years ago to plan for our tox studies and make sure that they bought into what we were doing in a way that we could move it forward. We went through a series of questions and together with our recommendations and their recommendations, we outlined a path for our toxicology studies, distribution studies, and what they wanted to see us do clinically. We were very conscious of all the FDA guidance. Overall, we had a very smooth interaction with the FDA as it related to our IND clearance.

Since it’s the very first human trial of cellular reprogramming, you would think they would be extremely cautious to the point of seriously slowing you down, but you’re saying it was smooth sailing?

Our experience was very collaborative and positive. We have a lot of data that we walked into the room with supporting the safety profile. We had data in mice, data in non-human primates. We had our IND studies. We walked in with a lot of safety data, and I think that really helped.

Do you think this signals a broader change in the FDA’s attitude toward longevity therapies in general?

It’s hard for me to say. It’s a one-off, right? We haven’t put seven things through the FDA, so it’s hard to get a bigger picture of what this means for them. We’re pleased that for what we did, it was positively perceived and most importantly, we got to our “may proceed” letter without any major issues.

If we look past the indications you’re currently working with, what’s next for Life Biosciences?

We’ve already talked publicly about having nice data on reprogramming in the liver, which is quite exciting. We’re continuing to work on the liver, and you may see in the next few months a little more information on some other indications we’re working on. We’re excited that we’re continuing to achieve proof of concepts across a range of indications.

This is an example of the very earliest stages of research leading to drug discovery, the identification of a potential target protein, here CUL5, that can be manipulated to change cell metabolism in a specific way, here meaning a reduction in the amount of tau protein in the cell. Aggregation of altered tau is a feature of late stage Alzheimer's disease, a cause of cell dysfunction and death in the brain. Reducing tau levels is one possible approach to the problem, though given that tau has a normal and necessary function in the brain, it may not be the best possible approach. At this stage, researchers do not know how CUL5 functions to affect tau levels, and thus a good deal of further work stands between the present discovery and the emergence of any practical outcome.

Aggregation of the protein tau defines tauopathies, the most common age-related neurodegenerative diseases, which include Alzheimer's disease and frontotemporal dementia. Specific neuronal subtypes are selectively vulnerable to tau aggregation, dysfunction, and death. However, molecular mechanisms underlying cell-type-selective vulnerability are unknown. To systematically uncover the cellular factors controlling the accumulation of tau aggregates in human neurons, we conducted a genome-wide CRISPR interference screen in induced pluripotent stem cell (iPSC)-derived neurons.

In comparison to other tau screens previously reported in the literature, our data have broadly similar patterns of hit genes. A previous genome-wide screen for modifiers of tau levels performed in SHY5Y cells has several shared classes of genetic modifiers. Surprisingly, this screen identified CUL5 as a negative modifier of tau levels. Since CUL5 regulates hundreds of substrates, it is not surprising that CUL5 knockdown has different phenotypes in different contexts.

We find CUL5 expression to be correlated with resilience in tauopathies along with genes encoding CUL5 interactors, including ARIH2 and SOCS4. However, the molecular mechanisms by which CUL5 affects neuronal vulnerability in AD remains to be identified. A broad distribution of CUL5 expression is seen in different neuronal subtypes in the Seattle Alzheimer's Disease Brain Cell Atlas suggesting that CUL5 may modulate disease vulnerability via multiple mechanisms. For instance, it is possible that CUL5 expression affects vulnerability via tau ubiquitination. But, considering CUL5's known role in immune signaling, another possibility is that CUL5 expression affects vulnerability via the neuro-immune axis.

Link: https://doi.org/10.1016/j.cell.2025.12.038

Parkinson's disease is driven by the spread of misfolded α-synuclein through the brain. The most evident symptoms result from the death and dysfunction of motor neurons, caused by the presence of misfolded α-synuclein. Once α-synuclein misfolds, it is capable of inducing other molecules of α-synuclein to misfold in the same way, and this dysfunction can slowly spread from cell to cell. In recent years, researchers have shown that in a sizable fraction of Parkinson's disease cases misfolded α-synuclein first emerges in the intestines and then spreads to the brain. Here, researchers uncover more of the mechanisms by which this transmission takes place, with an eye to finding ways to intervene in the earliest stages of the condition in order to prevent later consequences.

Emerging evidence suggests that Parkinson's disease (PD) may have its origin in the enteric nervous system (ENS), from where α-synuclein (αS) pathology spreads to the brain. Decades before the onset of motor symptoms, patients with PD suffer from constipation and present with circulating T cells responsive to αS, suggesting that peripheral immune responses initiated in the ENS may be involved in the early stages of PD. However, cellular mechanisms that trigger αS pathology in the ENS and its spread along the gut-brain axis remain elusive.

Here we demonstrate that muscularis macrophages (ME-Macs), housekeepers of ENS integrity and intestinal homeostasis, modulate αS pathology and neurodegeneration in models of PD. ME-Macs contain misfolded αS, adopt a signature reflecting endolysosomal dysfunction and modulate the expansion of T cells that travel from the ENS to the brain through the dura mater as αS pathology progresses. Directed ME-Mac depletion leads to reduced αS pathology in the ENS and central nervous system, prevents T cell expansion and mitigates neurodegeneration and motor dysfunction, suggesting a role for ME-Macs as early cellular initiators of αS pathology along the gut-brain axis. Understanding these mechanisms could pave the way for early-stage biomarkers in PD.

Link: https://doi.org/10.1038/s41586-025-09984-y