Murrall, K. | bioRxiv Science

bioRxiv2025

Small things matter: Lack of extra-islet beta cells in Type 1 diabetes

Recent 3D analyses reported abundant, small beta-cell-rich endocrine objects (EOs) in the human pancreas. Here, we assessed morphological parameters of >262,000 EOs in pancreas sections from 220 donors with or without type 1 diabetes (T1D), ranging in age and disease duration. We observe many insulin (Ins)+/glucagon (Gluc)-EOs in donors without diabetes. Their relative contribution to the total endocrine area is greatest in early life (0-2y) but reduces thereafter. Strikingly, we show the virtual absence of Ins+Gluc- EOs in individuals with T1D, where only the medium and large EOs retain beta cells. We also report a lower EO density in T1D, especially in individuals diagnosed in early life. These findings suggest that extra-islet beta cells are impacted in the development of T1D, and their early loss is a characteristic feature. This new understanding has important implications for defining beta-cell mass, which may inform future screening and treatment strategies in T1D. HighlightsO_LIThe present extensive 2D studies confirm and extend recent 3D analyses of human pancreata, demonstrating that 50% of endocrine objects (EOs) are much smaller than classical islets of Langerhans and consist predominantly of beta cells (Ins+). C_LIO_LISmall insulin+ EOs comprise the largest proportion of the total endocrine area in early childhood and persist throughout the life course in donors without diabetes. C_LIO_LIThere is a shift towards larger EO size with increasing age, with the most pronounced changes in size occurring in the first few years of life. C_LIO_LISmall Ins+ EOs are virtually absent in individuals with type 1 diabetes, while the persisting EOs with beta cells are larger, suggesting a selective destruction of beta cells in small EOs. C_LIO_LIDevelopment of type 1 diabetes, particularly at an early age, is associated with fewer larger EOs in adulthood. This implies that the lack or early destruction of small Ins+ EOs may be detrimental to the generation of larger EOs. C_LI

pathology↗

bioRxiv2023

Developmentally dynamic changes in DNA methylation in the human pancreas

Development of the human pancreas requires the precise temporal control of gene expression via epigenetic mechanisms and the binding of key transcription factors. We quantified genome-wide patterns of DNA methylation in human fetal pancreatic samples from donors aged 6 to 21 post-conception weeks. We found dramatic changes in DNA methylation across pancreas development, with >21% of sites characterized as developmental differentially methylated positions (dDMPs) including many annotated to genes associated with monogenic diabetes. An analysis of DNA methylation in postnatal pancreas tissue showed that the dramatic temporal changes in DNA methylation occurring in the developing pancreas are largely limited to the prenatal period. Significant differences in DNA methylation were observed between males and females at a number of autosomal sites, with a small proportion of sites showing sex-specific DNA methylation trajectories across pancreas development. Pancreas dDMPs were not distributed equally across the genome, and were depleted in regulatory domains characterized by open chromatin and the binding of known pancreatic development transcription factors. Finally, we compared our pancreas dDMPs to previous findings from the human brain, identifying evidence for tissue-specific developmental changes in DNA methylation. To our knowledge, this represents the most extensive exploration of DNA methylation patterns during human fetal pancreas development, confirming the prenatal period as a time of major epigenomic plasticity.

genomics↗