Lab Members

Principal Investigators

The Holt / Géléoc Lab operates with a non-conventional model.  We have one lab run by two principle investigators,

Jeffrey R. Holt and Gwenaelle, S.  Géléoc.  The arrangement works well as maintenance of a single lab helps to minimize expenses, while having two PIs facilitates scientific output.   Furthermore, while one PI is busy writing grants or manuscripts, the other can be in the lab doing experiments or working with lab members.  

Jeffrey R. Holt, Ph.D., Professor

I earned my doctorate from the Department of Physiology at the University of Rochester in 1995.  For my thesis work I studied inward rectifier potassium currents in saccular hair cells in Ruth Anne Eatock's lab.  I went on to a post-doctoral position in the Neurobiology Department at Harvard Medical School, where I characterized transduction and adaptation in vestibular hair cells and developed an adenoviral vector system to transfect cultured hair cells.  My first faculty position was at the University of Virginia.  In July, 2011 the lab moved to Boston Children’s Hospital / Harvard Medical School. I am currently a Professor in the Departments of Otolaryngology and Neurology in the F.M. Kirby Neurobiology Center where I am involved with graduate and medical student teaching; I am a member of the Harvard Medical School, Program in Neuroscience and the Harvard/MIT Program in Speech and Hearing Bioscience and Technology.  As one of two principle investigators for the lab, I write grants and manuscripts for publication, supervise and mentor lab members and make time to work on my own research project.  I am currently working on several projects:  1) I am investigating the function of TMC genes in hair cells using viral vectors to deliver wild-type and mutant channel genes and 2) I am interested in identifying other genes and proteins required for hair cell mechanosensory transduction, and

3) I am working to develop inner ear gene therapy for patients with genetic hearing loss. 

Hobbies:  Working late, playing with my kids, sailing, kite surfing, red wine, soccer, astrophotography.                                            Jeff's CV:


Gwenaelle S. Géléoc, Ph.D., Associate Professor

I was born in France and moved to the United States in Fall of 1999.  My passion for inner ear research began as an undergraduate student at the University of Montpellier (France) when I first saw a sensory hair cell under the

wonderful scientists including Corne Kros (Sussex University, UK), Guy Richardson (Sussex University, UK), Jonathan Ashmore (UCL, UK) and David Corey (HHMI, Harvard Medical School, USA). During my graduate work I developed a preparation which allowed me to record the first mechanotransduction currents from vestibular hair cells of the mammalian inner ear (Géléoc et al. 1996, 1997).  I realized that there was much to be learned by analyzing the pattern of functional developmental of inner ear hair cells around the time of birth. An obvious prerequisite for understanding vestibular and auditory disorders is knowledge of how hair cells develop in the normal state. Hair cells of the inner ear have the critical role of converting sound and head movement information into electrical signals which are transmitted to the brain.  Precisely how and when hair cells acquire mechanosensitivity is a major focus of my ongoing research. As an Assistant Professor at Boston Children’s Hospital I am also interested in the functional disruptions that are caused by mutations in hair cell genes, particularly those that cause congenital auditory and vestibular disorders in humans.  Armed with a better understanding of hair cell function and dysfunction, I aim to identify methods to protect or restore function in the sensory cells of the inner ear.                                   


Hobbies: Doing art work, cooking (and eating), sailing, hiking and skiing.


Olga Shubina-Oleinik, Ph.D., Post-Doctoral Fellow

I was born and grew up in Belarus. In 2011, I graduated from the International Sakharov Environmental University with a Bachelor's Degree in Biomedical Science. I received my Ph.D. degree at the Institute of Genetics and Cytology NAS of Belarus in 2015.  My Ph.D. project was dedicated to studying the genetics of non-syndromic hearing loss caused by both nuclear and mitochondrial mutations. I’ve also participated in developing a complex program of audiological and genetic testing of sensorineural hearing loss in children.  During this work I realized how complicated deafness can be, and how important it is to find treatment for hearing loss and improve people's lives.  In the spring of 2016, I had  the great opportunity to join the Holt/Géléoc Lab and continue my specialization in the field of hearing problems with a focus on developing  approaches to treat hearing impairment by gene therapy.
Hobbies: reading, dancing, yoga, writing sketches and traveling.


Irina Marcovich, Ph.D., Post-Doctoral Fellow

I was born and raised in Argentina. I got my Biology degree in 2014 at the Universidad de Buenos Aires and did my Ph.D. in the Laboratory of Physiology and Genetics of Hearing, led by Dr. Belen Elgoyhen (INGEBI-CONICET). My project aim was to study the evolutionary history of nicotinic cholinergic receptor subunits, particularly of the α9 and α10 nicotinic subunits which are expressed in the hair cells of the vertebrate inner ears. I became fascinated by the variety of mechanisms displayed by living organisms which allowed them to expand their hearing range, fine tune and amplify sound stimuli. I joined the Holt/Geleoc lab during the summer of 2019 to study evolution of mechanotransduction in the inner ear.


Hobbies: acting, singing, yoga, music and travel.​


Stephanie Mauriac, Ph.D., Post-Doctoral Fellow

I grew up in Bordeaux, France. In 2015, I received my undergraduate degree from the University of Bordeaux in cellular biology and physiopathology. My interest for the inner ear began when I join the lab of Dr. Mireille Montcouquiol and Dr. Nathalie Sans in Bordeaux as a PhD student.  During my PhD, I studied a very rare pathology, called the Chudley McCullough Syndrome, characterized by early onset sensorineural deafness and brain anomalies. During this project, I learned different technics including biochemistry, Immunocytochemistry, surgery and dissection that permit us to clarify the etiology and identify a new molecular basis of this pathology. During this exciting project, I realized how this work is essential to find a treatment for these patients in order to improve their lives. After receiving my PhD degree in June, 2019, I had the great opportunity to join the lab of Dr. Jeffrey Holt and Dr. Gwenaelle Geleoc in October 2019 to continue in hearing research. My goal is to discover and develop approaches to restore auditory function by gene therapy in models of human deafness.


Hobbies : traveling, cooking, sewing, reading, music, movies


Wang Zheng, Ph.D., Post-Doctoral Fellow

I was born and grew up in the central part of China and graduated from Beijing Institute of Technology (BIT) with a B.A. in Biotechnology in 2008. Then I went to Wuhan University for a master’s degree in Microbiology, during which I developed a strong interest in ion channel proteins. In 2011, I moved to Canada and joined Dr. Xing-Zhen Chen's lab at University of Alberta to study gating mechanisms of polycystin ion channels, which were mutated in human autosomal dominant polycystic kidney disease. After receiving my PhD degree in 2017, I continued to pursue my interests in ion channels by joining Slav Bagriantsev's lab at Yale University where I studied inactivation mechanisms of mechanosensitive Piezo ion channels and how their inactivation processes are regulated by temperature. My research interests then drove me to join the Holt/Geleoc group in 2019 to explore mechano-electrical transduction (MET) apparatus in the inner ear. My goal is to figure out how the MET channels convert mechanical force into electrical signals, which would establish a foundation to develop therapeutic treatment for hearing loss.


Hobby: Skiing, fishing, hiking, traveling, music, reading



Evan Ratzan, Post-Doctoral Fellow

I grew up in the Rocky Mountains of Colorado but headed east to Amherst, MA where I obtained my Bachelor's degree in Cognitive Neuroscience from Hampshire College in 2009. My passion for neuroscience propelled me through a dual-degree program at the University of Utah where I received a Master's in Clinical Investigations and Ph.D. in Neuroscience. I worked in the lab of Dr. Michael R. Deans examining mechanisms of cell polarity acquisition in the developing vestibular system. This work lead to the interesting discovery that Fgf8 expression is a specific and perhaps the earliest marker of Type-I vestibular hair cell identity thus far identified. My graduate work also identified important factors downstream from Emx2  which contribute to regional specification within the developing vestibular maculae. My graduate experience included a variety of molecular biology techniques including RNAseq, FISH, mouse genetics, immunohistochemistry, and more which I was excited to apply to scientific questions with a clinically relevant focus. I was fortunate to join the Holt/Géléoc lab where I focus on molecular mechanisms of vestibular and auditory pathophysiology.


Hobbies: Rock and ice climbing, snowboarding, music, drawing, painting, and reading.


Stephanie Rouse, Research Technologist

I was born and raised in Colorado Springs. I graduated from Grinnell College with a BA in history and biology. While there, I studied DNA damage response in gram-negative bacteria. My familiarity with molecular biology paired with an interest in neuroscience led me to the lab of Dr. Dylan Chan at UCSF, where I developed great passion for the inner ear.  In Dr. Chan’s lab, we studied calcium dynamics, the role of Connexin 26 and gap junctions in hearing and deafness. Much of our work assessed ER stress as an early mediator of cellular stress in the cochlea and common targetable mechanism in a range of hearing loss.  I am incredibly excited to continue my study of the pathophysiology and genetics of sensorineural hearing loss as a member of the Holt/Geleoc lab.


Hobbies: Competitive running, talking about the cochlea, all things out of doors, reading, spending time with family. 



Nikko Baer, Research Assistant

I graduated from Carleton College in 2020 with a B.A. in Biology and minors in Biochemistry and Neuroscience. After studying the development of the cranial nerves ‒ first at Carleton and then in the Engle Lab at Boston Children’s Hospital ‒ I moved downstairs to Holt/Geleoc Lab in the summer of 2020. I am now characterizing novel mutant mouse lines with the hope of developing gene therapies to treat hearing loss. Outside of the lab, I am working on an FM Kirby Center Equity, Diversity, and Inclusion initiative to increase faculty diversity at BCH.


Hobbies: Hiking, reading, baking, board games



Tessa Barrett, Research Assistant

I graduated in 2020 from the University of Vermont with a Bachelor's in Communication

Sciences and Disorders and a Minor in Behavioral Change Health Studies. My studies

focused on clinical audiology and speech pathology. Due to a family history of hearing

loss, I combine an appreciation for deaf culture with a passion for research into the

causes and cures for degenerative hearing loss. I am new to research and excited to

learn about genetic and molecular approaches to studying hearing loss. Thus far, I have

enjoyed dissecting and imaging cochleas (right). 

Hobbies:  OneWheeling, knitting, playing the guitar, snowboarding, and reading.

Margot Madison, High School Intern

I am a current Senior at Newton South High School interested in Neurobiology. My initial curiosity stemmed from an interest in how organisms interact with their environment via sensory inputs, specifically through sight and sound. I soon became fascinated by the biological mechanics that make processing sensory stimuli possible, particularly the molecular and cellular mechanisms of hearing, and how treatments are developed for hearing loss. In the Holt/Géléoc lab, I am excited to learn more about the auditory system and the process of scientific research as a whole.


Hobbies: Running, hiking, cooking, and gardening,  

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For a list of previous lab members please visit:  

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