Seminars

Mariana Wolfner presents research on the molecular changes in eggs, sperm, and females that coordinate successful reproduction, drawing on genetic and physiological studies of fertilization. This NIH Wednesday Afternoon Lecture Series event is offered in person and through NIH VideoCast.

Anne Ferguson-Smith examines the layer of epigenetic information that influences how the DNA sequence is used. Research on this layer has changed understanding of genome function, responses to the environment and possible inheritance beyond DNA sequence alone. The lecture considers how epigenetics affects genes and contributes to modern medicine, while asking which widely held claims are supported by evidence and which deserve renewed scrutiny.

Pluripotent cells, including embryonic stem (ES) and induced pluripotent stem (iPS) cells, are used to investigate the genetic and epigenetic underpinnings of human diseases such as Parkinson’s, Alzheimer’s, autism, and cancer. Mechanisms of somatic cell reprogramming to an embryonic pluripotent state are explored, utilizing patient-specific pluripotent cells to model and analyze neurodegenerative diseases.

Victor Ambros and Gary Ruvkun recount how studies of developmental timing in the nematode C. elegans revealed a new mechanism for regulating genes. The lectures follow the genetic analysis of lin-4 and lin-14, the discovery that a regulatory gene could produce a short non-coding RNA, and the connection between that RNA and complementary sequences in a target messenger RNA. They then examine how the discovery of additional microRNAs, including conserved regulators, changed a seemingly specialised worm finding into a widespread principle of gene regulation. The programme explains how small RNAs influence protein production after transcription and how experiments in a model organism exposed a regulatory system important across multicellular life.

Neurodevelopmental disorders (NDDs) impose a global burden, affecting an increasing number of individuals. While some causative genes have been identified, understanding the human-specific mechanisms involved in these disorders remains limited. Traditional gene-driven approaches for modeling brain diseases have failed to capture the diverse and convergent mechanisms at play. Centrosomes and cilia act as intermediaries between environmental and intrinsic signals, regulating cellular behavior. Mutations or dosage variations disrupting their function have been linked to brain formation deficits, highlighting their importance, yet their precise contributions remain largely unknown. Hence, we aim to investigate whether the centrosome/cilia axis is crucial for brain development and serves as a hub for human-specific mechanisms disrupted in NDDs. Towards this direction, we first demonstrated species-specific and cell-type-specific differences in the cilia-genes expression during mouse and human corticogenesis. Then, to dissect their role, we provoked their ectopic overexpression or silencing in the developing mouse cortex or in human brain organoids. Our findings suggest that cilia genes manipulation alters both the numbers and the position of NPCs and neurons in the developing cortex. Interestingly, primary cilium morphology is disrupted, as we find changes in their length, orientation and number that lead to disruption of the apical belt and altered delamination profiles during development. Our results give insight into the role of primary cilia in human cortical development and address fundamental questions regarding the diversity and convergence of gene function in development and disease manifestation. It has the potential to uncover novel pharmacological targets, facilitate personalized medicine, and improve the lives of individuals affected by NDDs through targeted cilia-based therapies.

During life, a variety of specialized cells arise to grant the right and timely corrected functions of tissues and organs. Regulation of chromatin in defining specialized genomic regions (e.g. enhancers) plays a key role in developmental transitions from progenitors into cell lineages. These enhancers, properly topologically positioned in 3D space, ultimately guide the transcriptional programs. It is becoming clear that several pathologies converge in differential enhancer usage with respect to physiological situations. However, why some regulatory regions are physiologically preferred, while some others can emerge in certain conditions, including other fate decisions or diseases, remains obscure. Schinzel-Giedion syndrome (SGS) is a rare disease with symptoms such as severe developmental delay, congenital malformations, progressive brain atrophy, intractable seizures, and infantile death. SGS is caused by mutations in the SETBP1 gene that results in its accumulation further leading to the downstream accumulation of SET. The oncoprotein SET has been found as part of the histone chaperone complex INHAT that blocks the activity of histone acetyltransferases suggesting that SGS may (i) represent a natural model of alternative chromatin regulation and (ii) offer chances to study downstream (mal)adaptive mechanisms. I will present our work on the characterization of SGS in appropriate experimental models including iPSC-derived cultures and mouse.

The Hsieh lab focuses on the mechanisms that promote neural stem cell self-renewal and differentiation in embryonic and adult brain. Using mouse models, video-EEG monitoring, viral techniques, and imaging/electrophysiological approaches, we elucidated many of the key transcriptional/epigenetic regulators of adult neurogenesis and showed aberrant new neuron integration in adult rodent hippocampus contribute to circuit disruption and seizure development. Building on this work, I will present our recent studies describing how GABA-mediated Ca2+ activity regulates the production of aberrant adult-born granule cells. In a new direction of my laboratory, we are using human induced pluripotent stem cells and brain organoid models as approaches to understand brain development and disease. Mutations in one gene, Aristaless-related homeobox (ARX), are of considerable interest since they are known to cause a common spectrum of neurodevelopmental disorders including epilepsy, autism, and intellectual disability. We have generated cortical and subpallial organoids from patients with poly-alanine expansion mutations in ARX. To understand the nature of ARX mutations in the organoid system, we are currently performing cellular, molecular, and physiological analyses. I will present these data to gain a comprehensive picture of the effect of ARX mutations in brain development. Since we do not understand how human brain development is affected by ARX mutations that contribute to epilepsy, we believe these studies will allow us to understand the mechanism of pathogenesis of ARX mutations, which has the potential to impact the diagnosis and care of patients.

The Cepko lab investigates the mechanisms that direct development of the central nervous system (CNS) of vertebrates, with a focus on the retina. These studies have revealed that the retina has distinct types of progenitor cells that are biased, or committed, to produce distinct types of daughter cells in terminal divisions. The gene regulatory networks that underlie these cell fate choices are being studied by analysis of both gene function and cis-regulatory networks. New methods that enable these studies have been developed, including high throughput enhancer assays and quantitative, inexpensive and sensitive multiplex in situ hybridization methods.