Biology subjects

Holzenberger, M.

Publications and source records attributed to Holzenberger, M..

4 recordsLinked to original sources

bioRxiv2024

The insulin / IGF axis is critically important controlling gene transcription in the podocyte.

Signalling to the podocyte via the structurally related insulin receptor (IR) or insulin-like growth factor 1 receptor (IGF1R) is important for podocyte function. This study sought to elucidate the compound role of the insulin/IGF1 axis in podocytes using transgenic mice and cell culture models deficient in both receptors. Podocyte specific IR/IGF1R knockdown mice developed a severe kidney phenotype with albuminuria, glomerulosclerosis and renal failure with death occurring in some mice between 4 and 24 weeks. Simultaneous knockdown of both receptors in cultured podocytes resulted in >50% cell death by 7 days. Proteomic analysis revealed a striking downregulation of spliceosome-related proteins in IR/IGF1R knockdown podocytes with long-read RNA sequence data indicating an increased fraction of transcripts with intron retention/premature termination codons in these cells. Furthermore, phospho-proteomic analysis revealed multiple insulin / IGF1 induced spliceosomal post-translational protein and kinase modifications suggesting dynamic control of this system. This study underlines the importance of podocyte insulin/IGF signalling demonstrating a novel role for this extrinsic hormonal signalling axis in regulating gene transcription in this cell type.

cell biology↗

bioRxiv2023

On growth and form of the mammary gland: Epithelial-mesenchymal interactions in embryonic mammary gland development

Mammary gland is a unique organ that undergoes dynamic alterations throughout a females reproductive life, making it an ideal model for developmental, stem cell and cancer biology research. Mammary gland development begins in utero and proceeds via a quiescent bud stage before the initial outgrowth and subsequent branching morphogenesis. How mammary epithelial cells transit from quiescence to an actively proliferating and branching tissue during embryogenesis and, importantly, how the branch pattern is determined remain largely unknown. Here we provide evidence indicating that epithelial cell proliferation, segregation into basal and luminal lineages that characterize the postnatal mammary duct, and onset of branching are independent processes, yet partially coordinated by the Eda signaling pathway. By performing heterotypic and heterochronic epithelial-mesenchymal recombination experiments between mammary and salivary gland tissues and ex vivo live imaging, we demonstrate that unlike previously concluded, the mode of branching is an intrinsic property of the mammary epithelium while the growth pace and density of the mammary ductal tree are governed by the mesenchyme. Transcriptomic profiling and ex vivo and in vivo functional studies disclose that mesenchymal Wnt/{beta}-catenin signaling, and in particular IGF-1 downstream of it critically regulate mammary gland growth. These results underscore the general need to carefully decompose the different developmental processes producing branched organs.

developmental biology↗

bioRxiv2022

The developmental basis for scaling of mammalian tooth size

When evolution leads to differences in body size, organs generally scale along. A well-known example of the tight relationship between organ and body size is the scaling of mammalian molar teeth. To investigate how teeth scale during development and evolution, we compared molar development in mouse and rat from initiation through final size. Whereas the linear dimensions of the rat first lower molar are twice that of the mouse molar, their shapes are largely the same. We found that scaling of the molars starts early, and that the rat molar is patterned equally as fast but in a larger size than the mouse molar. Using transcriptomics, we discovered that a known regulator of body size, insulin-like growth factor 1 (Igf1), is more highly expressed in the rat molars compared to the mouse molars. Ex vivo and in vivo mouse models demonstrated that modulation of the IGF pathway reproduces several aspects of the observed scaling process. Furthermore, analysis of IGF1-treated mouse molars and computational modeling indicate that IGF signaling scales teeth by simultaneously enhancing growth and by inhibiting the cusp patterning program, thereby providing a relatively simple mechanism for scaling teeth during development and evolution. Finally, comparative data from shrews to elephants suggest that this scaling mechanism regulates the minimum tooth size possible, as well as the patterning potential of large teeth.

developmental biology↗

bioRxiv2021

IGF1 Receptor Regulates Upward Firing Rate Homeostasis via the Mitochondrial Calcium Uniporter

Regulation of firing rate homeostasis constitutes a fundamental property of central neural circuits. While intracellular Ca2+ has long been hypothesized to be a feedback control signal, the molecular machinery enabling network-wide homeostatic response remains largely unknown. Here we show that deletion of insulin-like growth factor-1 receptor (IGF1R), a well-known regulator of neurodevelopment and ageing, limits firing rate homeostasis in response to inactivity, without altering the baseline firing rate distribution. Disruption of both synaptic and intrinsic homeostatic plasticity contributed to deficient firing rate homeostatic response. At the cellular level, a fraction of IGF1Rs was localized in mitochondria with the mitochondrial calcium uniporter complex (MCUc). IGF1R deletion suppressed spike burst-evoked mitochondrial Ca2+ (mitoCa2+) by weakening mitochondria-to-cytosol Ca2+ coupling. MCUc overexpression in IGF1R-deficient neurons rescued the deficits in spike-to-mitoCa2+ coupling and firing rate homeostasis. Our findings highlight IGF1R as a key regulator of the integrated homeostatic response by tuning mitochondrial temporal filtering. Decline in mitochondrial reliability for burst transfer may drive dysregulation of firing rate homeostasis in ageing and brain disorders associated with aberrant IGF1R / MCUc signaling.

neuroscience↗