SEARCH · Search PubMed

Results for “somatic expansion”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed2026

Loss of interruption in the HTT CAG repeat is associated with somatic expansion and loss of medium spiny neurons in Huntington's disease.

Synonymous loss-of-interruption variants in the expanded CAG repeat sequence of Huntingtin (HTT) accelerate the clinical onset and progression of Huntington's disease (HD). Medium spiny neurons (MSNs) are gradually lost in HD and undergo selective somatic CAG expansion, but it is unclear how somatic expansion relates to MSN pathology. Here, we show that MSNs with large (111-150 CAG) and very large (>150 CAG) somatic expansions are rare in early manifest HD but accumulate in proportion with duration of disease. In patients with the deleterious CAG-CCG loss-of-interruption (CAG-CCG LOI) modifier, the proportion of MSNs with large and very large expansions is increased ∼5-fold despite reduced small somatic expansions in blood, and caudate MSN counts are reduced. Our findings suggest that increased somatic CAG expansion contributes to accelerated striatal MSN pathology and onset of HD but that MSNs with very large genomic CAG expansions can persist among surviving neurons of the HD brain.

Huntington’s disease↗

PubMed2026

Targeting DNA mismatch repair in Huntington's disease.

Somatic expansion of the HTT CAG repeat is a key feature of Huntington's disease (HD) pathogenesis. Mismatch repair (MMR) enzymes drive this process through erroneous DNA repair, with variants in MMR genes modifying the onset and progression of disease features. Cell-type-specific CAG repeat sizing recently confirmed that elevated somatic expansion underlies the selective vulnerability of HD medium spiny neurons, with expansion beyond certain CAG thresholds associated with distinct stages of cellular pathogenesis. In this review, we synthesise insights from post-mortem brain tissue, cell systems, and mouse models, detailing key CAG repeat-length-dependent changes. In addition, we critically evaluate the MMR proteins MSH3, MLH3, and PMS1 as therapeutic targets for slowing somatic expansion and outline key safety considerations for emerging MMR-modulating approaches.

Huntington Disease↗

PubMed2026

Progressive cardiac phenotypes and reduced reversibility from long-term CUGexp RNA expression in a DM1 mouse model.

Myotonic dystrophy type 1 (DM1) is caused by an expanded CTG repeat in the DMPK gene, resulting in mutant transcripts that form expanded CUG (CUGexp) RNA foci and sequester muscleblind-like (MBNL) RNA-binding proteins. DM1 is multisystemic, with progressive worsening of disease manifestations in affected tissues. Disease progression is attributed to somatic expansion of the CTG repeats with age, resulting in production of CUGexp RNA with enhanced intrinsic toxicity due to increased MBNL sequestration. To determine the degree to which cardiac disease progression can occur independently of repeat expansion, we used a transgenic DM1 mouse model with inducible heart-specific expression of a stable, interrupted 960-CUG-repeat RNA. Sustained CUGexp RNA expression caused progressive cardiac enlargement, contractile dysfunction, conduction delay, myocardial fibrosis, and reduced survival, while MBNL-dependent splicing defects remained static, consistent with the stable repeat length. We also determined the degree of reversibility after different periods of CUGexp RNA expression by shutting off the repeat-containing transgene. Suppression of CUGexp RNA expression rescued cardiac abnormalities, but reversibility declined with longer exposure to the toxic RNA. These findings demonstrate that prolonged expression of stable CUGexp RNA drives progressive cardiac pathology, revealing a mechanism of disease progression in DM1 in addition to somatic expansion.

Animals↗

PubMed2025

Antisense oligonucleotide-mediated MSH3 suppression reduces somatic CAG repeat expansion in Huntington's disease iPSC-derived striatal neurons.

Expanded CAG alleles in the huntingtin (HTT) gene that cause the neurodegenerative disorder Huntington's disease (HD) are genetically unstable and continue to expand somatically throughout life, driving HD onset and progression. MSH3, a DNA mismatch repair protein, modifies HD onset and progression by driving this somatic CAG repeat expansion process. MSH3 is relatively tolerant of loss-of-function variation in humans, making it a potential therapeutic target. Here, we show that an MSH3-targeting antisense oligonucleotide (ASO) effectively engaged with its RNA target in induced pluripotent stem cell (iPSC)-derived striatal neurons obtained from a patient with HD carrying 125 HTT CAG repeats (the 125 CAG iPSC line). ASO treatment led to a dose-dependent reduction of MSH3 and subsequent stalling of CAG repeat expansion in these striatal neurons. Bulk RNA sequencing revealed a safe profile for MSH3 reduction, even when reduced by >95%. Maximal knockdown of MSH3 also effectively slowed CAG repeat expansion in striatal neurons with an otherwise accelerated expansion rate, derived from the 125 CAG iPSC line where FAN1 was knocked out by CRISPR-Cas9 editing. Last, we created a knock-in mouse model expressing the human MSH3 gene and demonstrated effective in vivo reduction in human MSH3 after ASO treatment. Our study shows that ASO-mediated MSH3 reduction can prevent HTT CAG repeat expansion in HD 125 CAG iPSC-derived striatal neurons, highlighting the therapeutic potential of this approach.

Huntington Disease↗

PubMed2026

Shared inheritance reveals landscape of somatic and germline cancer risk in TP53.

Pathogenic variants in TP53, the key tumor suppressor gene underlying Li-Fraumeni syndrome (LFS), are among the best-established causes of inherited cancer predisposition. However, large-scale sequencing has revealed that many apparently pathogenic TP53 variants detected in blood are the result of somatic clonal expansions, complicating risk interpretation. Using blood-derived whole-exome data from 469,391 UK Biobank participants, we combined the variant allele fraction (VAF) with haplotype-sharing analysis to distinguish germline and somatic TP53 variants. Germline variants were concentrated at sites linked to partial loss of p53 function and lower disease penetrance, whereas classic LFS alleles appeared to be predominantly somatically acquired. Classic LFS alleles at high VAF conferred markedly increased risk of hematological malignancy but not solid tumors, indicating an important contribution from large TP53-mutant clonal expansions. The prevalence of somatic clonal expansion also correlated with missense variant pathogenicity, suggesting that somatic activity provides an informative in vivo proxy for functional impact. These results provide new insights into TP53-associated cancer risk at the population level, demonstrate that somatic rather than germline risk predominates in middle-aged healthy adults, and provide a scalable framework for variant classification in large-scale population genomics.

Humans↗

PubMed2025

Polygenic variants in DNA repair genes are associated with neurodevelopmental disorders, regression and increased burdens of somatic variants and short tandem repeat expansions.

PURPOSE: Developmental regression, characterized by the loss of acquired milestones, occurs in some individuals with neurodevelopmental disorders (NDDs); yet, its molecular basis remains unclear. Studies suggest that DNA damage repair (DDR) genes, such as FAN1, may protect against neurological dysfunction by modulating the somatic stability of short tandem repeats (STRs). This study explores the contribution of DDR gene variants in NDD cases presenting with regression. METHODS: We analyzed 1087 NDD patients, focusing on those carrying variants in DDR genes and presenting regression. We assessed the sensitivity to DNA damage using mitomycin C on lymphoblastoid cells. Somatic variants and STR expansions were evaluated through high-depth short-read genome sequencing. To further investigate the pathogenetic role of STR expansions, we performed long-read genome sequencing on the most severely affected proband. RESULTS: Probands with regression carried multiple DDR gene variants, several within the Fanconi anemia pathway. Their lymphoblastoid cells showed increased sensitivity to mitomycin C-induced cytotoxicity compared with parental and control samples. Probands with severe phenotypes and regression exhibited an accumulation of somatic variants and STR instability, enriched in neurodevelopmental genes. CONCLUSION: Our findings suggest that polygenic DDR gene variants may contribute to developmental regression in NDDs by promoting the accumulation of somatic variants and STR expansions.

Humans↗

PubMed2026

Loss of Function Dnmt3a Mutation Leads to Aberrant Neutrophil Migration.

Clonal hematopoiesis (CH), an age-related expansion of somatically mutated hematopoietic clones, is associated with increased risk of severe infections including coronavirus disease (COVID)-19, yet the underlying mechanisms remain unclear. Here, we investigated the impact of Dnmt3a deficiency in a murine model of influenza A virus (IAV) pneumonia. Dnmt3a-deficient mice exhibited increased pulmonary viral burden and reduced neutrophil accumulation in IAV-infected lungs despite comparable circulating neutrophil numbers. Functional analyses of neutrophils showed impaired chemotactic migration in vitro, whereas maturation, antimicrobial enzyme content, and metabolic capacity were unchanged. Transcriptomic profiling revealed downregulation of pathways involved in chemotaxis, cytokine signaling, and cellular activation, including reduced expression of Cxcr1. Supporting the translational relevance of these findings, proteomic analysis of plasma from individuals with germline DNMT3A mutations (Tatton-Brown-Rahman syndrome) revealed alterations in proteins associated with cell migration and cytoskeletal dynamics. Collectively, our findings demonstrate that Dnmt3a loss compromises innate immune defense by impairing neutrophil migration in a cell-intrinsic manner, leading to ineffective pathogen clearance. This work provides mechanistic insight into how CH-associated mutations contribute to age-associated susceptibility to infection and highlights altered leukocyte trafficking as a potential therapeutic target in aging populations with CH.

Animals↗

PubMed2026

The HTT1a protein initiates HTT aggregation in a knock-in mouse model of Huntington's disease.

The mutation that causes Huntington's disease is a CAG repeat expansion in exon 1 of the huntingtin gene (HTT) that leads to an abnormally long polyglutamine tract in the huntingtin protein (HTT). Mutant CAG repeats are unstable and increase in size in specific neurons and brain regions with age, a phenomenon that constitutes the first step in the pathogenesis of the disease. In the presence of an expanded CAG repeat, cryptic polyadenylation (polyA) sites in intron 1 of the HTT pre-mRNA can become activated leading to the polyadenylation of a prematurely terminated transcript, HTT1a. This encodes the HTT1a protein, which is known to be very aggregation-prone and highly pathogenic. Given that the longer the CAG repeat the more HTT1a is generated, could the production of HTT1a be the mechanism through which somatic CAG repeat expansion exerts its pathogenic consequences? Resolving this issue is very important for the design of therapeutic approaches to lower huntingtin levels. We have used a clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 approach to prevent the production of HTT1a in a knock-in mouse model of Huntington's disease. All potential cryptic polyA sites were deleted from Htt intron 1 in HdhQ150 mice and colonies were established that were heterozygous for the intron 1 deletion on a mutant allele (HdhQ150ΔI) and heterozygous for the deletion on a wild-type allele (WTΔI). The CAG repeat sizes in the HdhQ150 and HdhQ150ΔI colonies were well-matched at approximately 195 CAGs. As predicted, the deletion of the cryptic polyA sites from Htt intron 1 prevented the generation of the Htt1a transcript in the HdhQ150ΔI mice. However, very low levels of the HTT1a protein were detected, which resulted from a Htt readthrough product of exon 1 and exon 2, that had retained the deleted intron and terminated at a cryptic polyA site in intron 2. HdhQ150, HdhQ150ΔI, wild-type and WTΔI mice were studied until 17 months of age. Immunohistochemical and homogeneous time-resolved fluorescence analysis showed that HTT aggregation in both HdhQ150 and HdhQ150ΔI brains contained HTT1a, but the dramatic decrease in soluble HTT1a levels in HdhQ150ΔI brains delayed the appearance of aggregated HTT1a by several months. Although this delay in aggregate pathology only partially reversed transcriptional dysregulation, the biomarkers neurofilament light polypeptide (NEFL) and breast regression protein 39 (BRP39) (YKL40) remained at wild-type levels in HdhQ150ΔI mice at 17 months of age. These data demonstrate that the production of HTT1a initiates HTT aggregation and that it is important to target HTT1a in huntingtin-lowering therapeutic strategies.

Animals↗

PubMed2025

SURROGATE SELECTION OVERSAMPLES EXPANDED T CELL CLONOTYPES.

Surrogate selection is an experimental design that without sequencing any DNA can restrict a sample of cells to those carrying certain genomic mutations. In immunological disease studies, this design may provide a relatively easy approach to enrich a lymphocyte sample with cells relevant to the disease response because the emergence of neutral mutations associates with the proliferation history of clonal subpopulations. A statistical analysis of clonotype sizes provides a structured, quantitative perspective on this useful property of surrogate selection. Our model specification couples within-clonotype birth-death processes with an exchangeable model across clonotypes. Beyond enrichment questions about the surrogate selection design, our framework enables a study of sampling properties of elementary sample diversity statistics; it also points to new statistics that may usefully measure the burden of somatic genomic alterations associated with clonal expansion. We examine statistical properties of immunological samples governed by the coupled model specification, and we illustrate calculations in surrogate selection studies of melanoma and in single-cell genomic studies of T cell repertoires.

Bayes’s rule↗

PubMed2025

PhyClone: accurate Bayesian reconstruction of cancer phylogenies from bulk sequencing.

MOTIVATION: Cancer is driven by somatic mutations that result in the expansion of genomically distinct sub-populations of cells called clones. Identifying the clonal composition of tumours and understanding the evolutionary relationships between clones is a crucial task in cancer genomics. Bulk DNA sequencing is commonly used for studying the clonal composition of tumours, but it is challenging to infer the genetic relationship between different clones due to the mixture of different cell populations. RESULTS: In this work, we introduce a new probabilistic model called PhyClone that can infer clonal phylogenies from bulk-sequencing data. We demonstrate the performance of PhyClone on simulated and real-world datasets and show that it outperforms previous methods in terms of accuracy and sample scalability. AVAILABILITY AND IMPLEMENTATION: Source code is available on Github at: https://github.com/Roth-Lab/PhyClone under the GPL v3.0 license.

Neoplasms↗

PubMed2024

The Genetic Determinants and Genomic Consequences of Non-Leukemogenic Somatic Point Mutations.

Clonal hematopoiesis (CH) is defined by the expansion of a lineage of genetically identical cells in blood. Genetic lesions that confer a fitness advantage, such as point mutations or mosaic chromosomal alterations (mCAs) in genes associated with hematologic malignancy, are frequent mediators of CH. However, recent analyses of both single cell-derived colonies of hematopoietic cells and population sequencing cohorts have revealed CH frequently occurs in the absence of known driver genetic lesions. To characterize CH without known driver genetic lesions, we used 51,399 deeply sequenced whole genomes from the NHLBI TOPMed sequencing initiative to perform simultaneous germline and somatic mutation analyses among individuals without leukemogenic point mutations (LPM), which we term CH-LPMneg. We quantified CH by estimating the total mutation burden. Because estimating somatic mutation burden without a paired-tissue sample is challenging, we developed a novel statistical method, the Genomic and Epigenomic informed Mutation (GEM) rate, that uses external genomic and epigenomic data sources to distinguish artifactual signals from true somatic mutations. We performed a genome-wide association study of GEM to discover the germline determinants of CH-LPMneg. After fine-mapping and variant-to-gene analyses, we identified seven genes associated with CH-LPMneg (TCL1A, TERT, SMC4, NRIP1, PRDM16, MSRA, SCARB1), and one locus associated with a sex-associated mutation pathway (SRGAP2C). We performed a secondary analysis excluding individuals with mCAs, finding that the genetic architecture was largely unaffected by their inclusion. Functional analyses of SMC4 and NRIP1 implicated altered HSC self-renewal and proliferation as the primary mediator of mutation burden in blood. We then performed comprehensive multi-tissue transcriptomic analyses, finding that the expression levels of 404 genes are associated with GEM. Finally, we performed phenotypic association meta-analyses across four cohorts, finding that GEM is associated with increased white blood cell count and increased risk for incident peripheral artery disease, but is not significantly associated with incident stroke or coronary disease events. Overall, we develop GEM for quantifying mutation burden from WGS without a paired-tissue sample and use GEM to discover the genetic, genomic, and phenotypic correlates of CH-LPMneg.

Journal Article↗

PubMed2025

Deciphering Clonal Hematopoiesis of Indeterminate Potential: Methods, Mechanisms, and Implications for Kidney Diseases.

CKD afflicts over 10% of US adults, with its prevalence increasing sharply with age. Clonal hematopoiesis of indeterminate potential (CHIP) is a common, genetically heterogeneous blood cell disorder characterized by the age-related clonal expansion of hematopoietic cells driven by leukemogenic somatic mutations yet without hematologic malignancy or dysplasia. While CHIP is a strong risk factor of future hematologic malignancy (estimated at approximately 0.5% per year, compared with <0.1% for those without CHIP), it is also linked to two-fold higher cardiovascular disease in epidemiologic, cell-based, and murine studies. However, more recent work has implicated CHIP with kidney outcomes, such as CKD as well as AKI, independent of traditional risk factors. This review covers the observations and proposed hypotheses linking CHIP and kidney disease. The review also underscores the need for further research to elucidate the distinct pathways through which CHIP may contribute to CKD and its comorbidities, considering the heterogeneity within CKD stages and etiologies, as well as whether CHIP is a causal driver of kidney disease or a marker of aging and comorbidity. Finally, we discuss the potential of anti-inflammatory treatments to mitigate CHIP's adverse effects on kidney health, aiming to improve management strategies for patients with CHIP-associated kidney diseases.

Humans↗

PubMed2026

Harnessing Endogenous Plasticity Rather than Reprogramming of Mature Cells Will Advance Regenerative Medicine, Cancer Treatment and Rejuvenation.

The successful culture of human embryonic stem (hES) cells from inner cell mass cells of blastocyst stage 'spare' embryos in 1998, followed by induced pluripotent stem (iPS) cells in 2006, which allowed somatic cells to be reprogrammed to pluripotency using the Yamanaka factors, transformed regenerative biology and inspired extensive global efforts towards developing pluripotent stem cell-based applications. However, hES and iPS cells, as well as organoids generated from them, largely retain fetal-like characteristics, which limits their relevance for clinical translation. Concurrently, the prevailing assumption published in leading journals that adult tissues lack endogenous stem cells has led to the belief that mature cells dedifferentiate and reprogram during in vivo regeneration upon chronic injury, and that the appearance of embryonic/fetal markers in diabetes, heart failure, cancer, and many other chronic disease states reflects dedifferentiation of mature cells. We suggest that the prevailing concepts of dedifferentiation and reprogramming, both in vitro and in vivo, require careful re-evaluation. Adult somatic cells possibly do not truly dedifferentiate, neither in vitro nor in vivo. Instead, tissue-resident, pluripotent, very small embryonic-like stem cells (VSELs) in multiple organs account for the observed biology. In vitro "reprogramming" responses to Yamanaka factors likely reflect selective activation and expansion of VSELs/early progenitors rather than the dedifferentiation/ reprogramming of mature adult somatic cells. Likewise, the embryonic/fetal-like signatures reported in multiple disease states including cancer reflect expansion of immature tissue-specific progenitors that arise from VSELs but fail to differentiate normally due to a damaged microenvironment in vivo. Therapeutic strategies involving transplantation of MSCs, MUSE cells, or their secreted exosomes improve disease outcomes, possibly by restoring the damaged niche that supports functional tissue repair by VSELs. Although direct evidence to support this is lacking at present, recognising the central role of VSELs/progenitors and their niche in maintaining tissue homeostasis in vivo could resolve existing roadblocks and guide more effective endogenous regenerative therapies for diseased tissues and age-related dysfunctions.

Humans↗

PubMed2026

Clonal haematopoiesis of indeterminate potential and epigenetic age acceleration: Systematic review and meta-analysis.

Clonal haematopoiesis of indeterminate potential (CHIP) represents somatic mutations in haematopoietic stem cells that drive clonal expansion. Epigenetic age acceleration (EAA), estimated from DNA methylation (DNAm) clocks, may capture age-related changes in haematopoiesis. This systematic review and meta-analysis was conducted to synthesise evidence on associations between CHIP and EAA and explore shared biological mechanisms that may underlie this relationship. Six databases were searched from January 1, 2011, to June 6, 2025, adhering to PRISMA 2020. Random-effects meta-analyses were performed. Five studies comprising 7483 individuals (ages 55-79, 67.1% female) assessing associations between CHIP and DNAm clocks were included. Across studies, CHIP individuals had higher EAA than no-CHIP individuals, and larger clones were associated with higher EAA. Meta-analysis of three cross-sectional studies (n = 6946) showed that CHIP had higher EAA versus no-CHIP for Horvath1Age IEAA (mean difference, MD=2.84 years, 95% confidence interval, CI: 1.49-4.19), HannumAge EEAA (MD=2.31 years, 95% CI: 1.14-3.49), PhenoAge (MD=1.84 years, 95% CI: 0.96-2.71), and GrimAge (MD=1.20 years, 95% CI: 0.80-1.61). Both DNMT3A- and TET2-mutated CHIP were associated with higher EAA with TET2-mutated CHIP showing larger effect sizes and more consistent associations than DNMT3A-mutated CHIP across DNAm clocks tested. Higher EAA may also act as an effect modifier for morbidity and mortality in CHIP. Larger longitudinal studies are needed to verify a temporal relationship and determine whether EAA provides incremental prognostic value for morbidity and mortality in CHIP.

Humans↗

PubMed2025

First clinical diagnosis of FAME3 via commercial Long-Read sequencing reveals mosaic repeat expansion in MARCHF6 gene.

Familial Adult Myoclonic Epilepsy type 3 (FAME3) is a rare autosomal dominant disorder characterized by cortical tremor and epilepsy, caused by a noncoding pentanucleotide repeat expansion (TTTTA/TTTCA)n in the MARCHF6 gene. Conventional genetic testing often fails to detect this expansion due to its repetitive structure and intronic location. We evaluated a 61-year-old woman with refractory myoclonic and generalized tonic-clonic seizures, whose prior genetic testing-including exome and genome sequencing-was non-diagnostic. Using PacBio HiFi long-read whole-genome sequencing and the tandem repeat genotyping tool TRGT, we identified a pathogenic MARCHF6 intronic expansion. The proband harbored one allele with 15 TTTTA repeats and a second allele with a compound expansion of 661 TTTTA and 12 TTTCA repeats. Three affected relatives shared similarly expanded alleles, but with increasing repeat size in the latter generations. Importantly, analysis using TRGT-instability revealed repeat mosaicism in all affected individuals, reflected by variability in motif counts across individual sequencing reads. This somatic heterogeneity may contribute to the phenotypic penetrance, variable expressivity and pleiotropism seen in FAME3 disease expression. To our knowledge, this is the first clinical diagnosis of FAME3 using a commercially available long-read sequencing platform, underscoring its diagnostic utility in resolving complex repeat expansion disorders and uncovering biologically relevant mosaicism.

Humans↗

PubMed2026

Measurable Residual Disease and the Unresolved Biology of Leukemic Stem Cells.

Measurable residual disease (MRD) testing has transformed the management of hematologic cancers by enabling detection of residual malignant cells after therapy. Current approaches rely on qPCR and next-generation sequencing to monitor leukemia-associated somatic mutations, while multiparameter flow cytometry identifies aberrant leukemic immunophenotypes. Although these methods provide valuable prognostic and therapeutic information, MRD negativity remains an imperfect surrogate for cure. Most MRD platforms evaluate CD45+, rapidly dividing leukemic populations and fail to detect quiescent cells that may survive cytotoxic therapies which efficiently target proliferating hematopoietic cells. Relapse frequently occurs despite deep molecular remission, suggesting persistence of rare leukemic stem cells (LSCs) that are intrinsically resistant to chemotherapy and targeted therapies. The paradox of relapse despite molecular remission could be explained by the presence of very small embryonic-like stem cells (VSELs) which are pluripotent, quiescent stem cells sitting at the top of cellular hierarchy in multiple adult tissues including bone marrow. A pluripotent VSEL divides through asymmetrical cell division to give rise to two cells of different sizes and fates, smaller cell is to self-renew while the bigger is lineage-restricted and tissue-committed progenitor which undergoes extensive epigenetic changes, divides rapidly and undergoes clonal expansion before further differentiation. Dysfunctions of VSELs initiate both solid and hematologic cancers. Based on this view, somatic mutations monitored during MRD assessment possibly represent downstream consequences of clonal expansion rather than the initiating drivers of disease persistence. Thus, exclusive monitoring of somatic mutations and CD45 + leukemic populations possibly overlook rare, small-sized, CD45- VSELs that contribute to therapeutic resistance and relapse.

Humans↗

PubMed1977

Mesodermal expansion after arrest of the edge in the area vasculosa of the chick.

To investigate whether mesodermal expansion in the area vasculosa is caused by tension produced by outward migration of cells either in the somatic mesoderm or at the mesodermal edge on an ectodermal substratum, stage 18--20 embryos were transferred to a culture dish. There mesodermal expansion proximal to an arrested edge could be compared with that proximal to a moving edge by measuring the amount of vascular elongation occurring in each. A proximo-distal gradient in vascular elongation rate was detected both in normal embryos in ovo and in explants. This gradient was reversed following arrest of the edge, and the rate of vascular elongation proximal to the arrested edge decreased to 60--70% of that proximal to a moving edge. Nearly all of the mesoderm producing this expansion was located in the proximal two-thirds of the area vasculosa, where vascular elongation rate on the stopped side of the explant was not significantly different from that on the moving side. Similar results were obtained in the absence of the ectoderm, and when liquid culture medium was used instead of semisolid medium. It is concluded that tensile force derived from mesodermal migration plays no role in expansion of the proximal two-thirds of the area vasculosa mesoderm.

Animals↗

PubMed2026

Telomere length and clonal hematopoiesis interact to influence outcomes in hematopoietic stem cell transplantation.

Clonal hematopoiesis (CH), the clonal expansion of a hematopoietic stem cell and its progeny driven by somatic mutations, has been associated with inferior survival outcomes among recipients of autologous stem cell transplants (ASCT). Leukocyte telomere length (LTL) has a complex but well-documented interaction with CH, but the impact of this interaction on stem cell transplantation has not been adequately examined. We measured LTL in graft cell DNA from 452 patients undergoing ASCT for myeloma, for whom targeted DNA sequencing for CH driver gene mutations was available. We interrogated clinical and longitudinal large-scale laboratory data for these patients to understand the impact of graft LTL on progression-free survival (PFS) and overall survival after transplantation, as well as blood count indices and their trajectories. In multivariate analyses, longer LTL was associated with increased PFS among patients without CH. However, this protective association was not seen in patients with CH. We also report that among patients with CH, longer LTL was associated with an increased red cell distribution width before myeloablative chemotherapy and after ASCT. Collectively, these data reveal hitherto undescribed interactions between LTL, CH, and ASCT outcomes.

Humans↗