Christina Gangemi

All Publications

• Modular Light-Emitting Diode Shelving Systems for Scalable Optogenetics. Methods in molecular biology (Clifton, N.J.) Gangemi, C. G., Janovjak, H. 2025; 2840: 231-244

  Abstract

  Optogenetic experiments rely on the controlled delivery of light to diverse biological systems. Impressive devices have been recently developed to stimulate cells and small animals with multiple wavelengths and intensities. However, existing hardware solutions are often limited to a single sample holder, and their design and cost can further limit scalability. This chapter describes an illumination system that is modular (through the use of accessible components) and scalable (through a shelving structure and low cost). Assembly and operation require no or minimal electrical engineering or programming expertise. Multi-intensity wavelength and temporal experiments can be performed in dozens of small and large samples. This chapter also introduces methods for temperature and light intensity measurements toward appropriate illumination conditions. This work aims to provide a greater level of accessibility and complementary opportunities for large-scale optogenetics in a broad range of biological samples.

  View details for DOI 10.1007/978-1-0716-4047-0_17

  View details for PubMedID 39724356

  View details for PubMedCentralID 6365057

• Optogenetics in Pancreatic Islets: Actuators and Effects DIABETES Gangemi, C. G., Janovjak, H. 2024; 73 (10): 1566-1582

  Abstract

  The islets of Langerhans reside within the endocrine pancreas as highly vascularized microorgans that are responsible for the secretion of key hormones, such as insulin and glucagon. Islet function relies on a range of dynamic molecular processes that include Ca2+ waves, hormone pulses, and complex interactions between islet cell types. Dysfunction of these processes results in poor maintenance of blood glucose homeostasis and is a hallmark of diabetes. Recently, the development of optogenetic methods that rely on light-sensitive molecular actuators has allowed perturbation of islet function with near physiological spatiotemporal acuity. These actuators harness natural photoreceptor proteins and their engineered variants to manipulate mouse and human cells that are not normally light-responsive. Until recently, optogenetics in islet biology has primarily focused on controlling hormone production and secretion; however, studies on further aspects of islet function, including paracrine regulation between islet cell types and dynamics within intracellular signaling pathways, are emerging. Here, we discuss the applicability of optogenetics to islets cells and comprehensively review seminal as well as recent work on optogenetic actuators and their effects in islet function and diabetes mellitus.

  View details for DOI 10.2337/db23-1022

  View details for Web of Science ID 001321521000014

  View details for PubMedID 38976779

  View details for PubMedCentralID PMC11417442

• CDK6 activity in a recurring convergent kinase network motif. FASEB journal : official publication of the Federation of American Societies for Experimental Biology Gangemi, C. G., Sabapathy, R. T., Janovjak, H. 2023; 37 (4): e22845

  Abstract

  In humans, more than 500 kinases phosphorylate ~15% of all proteins in an emerging phosphorylation network. Convergent local interaction motifs, in which ≥two kinases phosphorylate the same substrate, underlie feedback loops and signal amplification events but have not been systematically analyzed. Here, we first report a network-wide computational analysis of convergent kinase-substrate relationships (cKSRs). In experimentally validated phosphorylation sites, we find that cKSRs are common and involve >80% of all human kinases and >24% of all substrates. We show that cKSRs occur over a wide range of stoichiometries, in many instances harnessing co-expressed kinases from family subgroups. We then experimentally demonstrate for the prototypical convergent CDK4/6 kinase pair how multiple inputs phosphorylate the tumor suppressor retinoblastoma protein (RB) and thereby hamper in situ analysis of the individual kinases. We hypothesize that overexpression of one kinase combined with a CDK4/6 inhibitor can dissect convergence. In breast cancer cells expressing high levels of CDK4, we confirm this hypothesis and develop a high-throughput compatible assay that quantifies genetically modified CDK6 variants and inhibitors. Collectively, our work reveals the occurrence, topology, and experimental dissection of convergent interactions toward a deeper understanding of kinase networks and functions.

  View details for DOI 10.1096/fj.202201344R

  View details for PubMedID 36884374

• GILZ-dependent modulation of mTORC1 regulates spermatogonial maintenance. Development (Cambridge, England) La, H. M., Chan, A. L., Legrand, J. M., Rossello, F. J., Gangemi, C. G., Papa, A., Cheng, Q., Morand, E. F., Hobbs, R. M. 2018; 145 (18)

  Abstract

  Male fertility is dependent on spermatogonial stem cells (SSCs) that self-renew and produce differentiating germ cells. Growth factors produced within the testis are essential for SSC maintenance but intrinsic factors that dictate the SSC response to these stimuli are poorly characterised. Here, we have studied the role of GILZ, a TSC22D family protein and spermatogenesis regulator, in spermatogonial function and signalling. Although broadly expressed in the germline, GILZ was prominent in undifferentiated spermatogonia and Gilz deletion in adults resulted in exhaustion of the GFRα1+ SSC-containing population and germline degeneration. GILZ loss was associated with mTORC1 activation, suggesting enhanced growth factor signalling. Expression of deubiquitylase USP9X, an mTORC1 modulator required for spermatogenesis, was disrupted in Gilz mutants. Treatment with an mTOR inhibitor rescued GFRα1+ spermatogonial failure, indicating that GILZ-dependent mTORC1 inhibition is crucial for SSC maintenance. Analysis of cultured undifferentiated spermatogonia lacking GILZ confirmed aberrant activation of ERK MAPK upstream mTORC1 plus USP9X downregulation and interaction of GILZ with TSC22D proteins. Our data indicate an essential role for GILZ-TSC22D complexes in ensuring the appropriate response of undifferentiated spermatogonia to growth factors via distinct inputs to mTORC1.

  View details for DOI 10.1242/dev.165324

  View details for PubMedID 30126904