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Insulin deficiency distorts human pancreatic endocrine cell composition during development

ABSTRACT: Objective: The developmental effects of mutations in genes associated with monogenic diabetes on human pancreas development is not well understood. More specifically, if insulin gene recessive mutations influence the human endocrine lineage segregation still needs to be investigated. Methods: We generated a novel knock-in H2B-Cherry reporter human induced pluripotent stem cell (iPSCs) line expressing no insulin upon differentiation to stem cell-derived (SC-) β cells in vitro. This cell line enabled us to have a model mimicking the extremely reduced insulin levels in patients with recessive insulin mutations. We combined immunostaining, Western blotting and proteomics analysis to characterize the SC-islets from this iPSC line. Furthermore, we leveraged FACS analysis and imaging to explore the impact of insulin shortage on human endocrine cell induction, composition and proliferation. Results: We found that lack of insulin hampers insulin receptor (IR) signaling in SC-islets but increases the IR sensitivity. Furthermore, insulin deficiency showed no effects on human endocrine lineage induction. However, lack of insulin skewed the SC-islet cell composition. We found an increased in SC-β cell number at the expense of SC-α cell differentiation in the absence of insulin. Finally, insulin shortage reduced the rate of SC-β cell proliferation but had no impact of the expansion of SC-α cells. Conclusions: We provided evidence of the developmental impacts of reduced insulin levels on human β cell characteristics and endocrine lineage formation. These findings help to better understand the pathomechanisms of recessive insulin mutations during embryonic development and also shed some lights on the possible physiological function of this hormone coordinating human islet cell composition and architecture during endocrinogenesis.

INSTRUMENT(S): Orbitrap Exploris 480

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Pluripotent Stem Cell, Fibroblast

SUBMITTER: Natalie Krahmer

LAB HEAD: Natalie Krahmer

PROVIDER: PXD045366 | Pride | 2024-01-17

REPOSITORIES: Pride

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Project description:Pyruvate oxidase encoded by spxB is a major virulence factor in the human respiratory pathogen Streptococcus pneumoniae. During aerobic growth, SpxB synthesizes large amounts of H2O2 and acetyl phosphate, which can serve as a phosphoryl group donor to response regulators and be converted to ATP. SpxB is the main source of the millimolar concentrations of H2O2 produced and tolerated by pneumococcus, despite its lack of a catalase. We report here the first cis- and trans-acting regulatory elements for spxB transcription. These elements were identified in a genetic screen, similar to those used previously for phase variants, for spontaneous mutations that caused colonies of virulent serotype 2 strain D39 to change from a transparent to an opaque appearance. Six of the seven opaque colonies recovered (frequency of 3 x 10-5) were impaired for SpxB function. Modeling suggested that two mutations changed amino acids in SpxB required for FAD cofactor or subunit binding. One mutation deleted a cis-acting adjacent direct repeat required for optimal spxB transcription. The other three independent mutations created the same frameshift near the start of a trans-acting regulatory gene designated as spxR. The SpxR protein contains helix-turn-helix, CBS, and HotDog domains implicated in DNA, adenosine, and CoA compound binding, respectively, consistent with the idea that SpxR positively regulates spxB transcript amount in response to energy and metabolic state rather than oxidative state. Finally, microarray analyses of a null spxB or a spxR mutant revealed the presence of a new oxidative stress response in pneumococcus and unexpectedly demonstrated that SpxR strongly positively regulates the transcript amount of the strH exoglycosidase gene, which like spxB, has been implicated in host colonization. Keywords: genetic modification Bacterial strains were grown exponentially in rich (BHI) media at 37C and an atmosphere of 5% CO2, and were processed as described in the related Sample records. Samples were collected from three independent biological replicates and included one dye swap. Data were normalized using the Lowess (subgrid) method without background subtraction.

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Insulin deficiency distorts human pancreatic endocrine cell composition during development

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