Project Summary
There are two critical pacemakers for life: the cardiac pacemaker and the breathing pacemaker, the
preBötzinger Complex (preBötC). The preBötC is a cluster of ~3000 neurons in the brainstem that are
cyclically active, with each burst of activity initiating a breath. In contrast to the cardiac pacemaker, the
molecular and cellular basis of breathing rhythm generation remains unknown, as do diseases associated with
it, such as central sleep apnea and sudden infant death. The prevailing model of preBötC rhythm generation,
called the `group-pacemaker' model, proposes that each breath is triggered by an emergent preBötC network
phenomena. An important assumption of this model is that there are not dedicated breath-initiating neurons.
However, based on the observed variety of preBötC neuron firing patterns, including ones that fire just before
each breath (pre-inspiratory), and the unexpected molecular and functional diversity of the preBötC neurons I
discovered during my Ph.D., I hypothesize that, as in the heart, there are specific neurons that initiate each
breath, breathing pacemaker neurons, and propose to identify and characterize them in this research
proposal. As a UCSF Sandler Fellow and recipient of the Early Independence Award, I plan to first
comprehensively map preBötC cell types with single cell gene expression analysis and identify candidate
breathing pacemaker neurons by their expression of the same ion channels important for cardiac pacemaking.
Additionally, I plan identify candidate breath-initiating neurons by their anticipated activity during breathing
(pre-inspiratory) and their autonomous, rhythmic activity in vitro (pacemaker activity). Lastly, I will identify
candidate pacemakers by their proposed connectivity to ~175 preBötC neurons I identified in my Ph.D. that
receive breathing pacemaker activity. I predict that these three independent approaches will converge on the
same preBötC subtypes, the presumed breathing pacemaker neurons and I will then use intersectional genetic
strategies to test if the identified neurons have breathing pacemaker properties: autonomous rhythmic activity,
pre-inspiratory activity, ability to initiate a breath, and requirement for breathing. The molecular and functional
identification of respiratory pacemaker neurons will be a transformative discovery, leading to the eventual
resolution of how respiratory rhythms and arrhythmias, some of the most deadly diseases in infants, are
generated. This mechanistic understanding of breathing rhythm generation will provide an avenue to develop
pharmacological approaches to control ventilation, which would impact multiple medical fields, especially
neonatology and critical care medicine. In my recent Ph.D. work, I have demonstrated extraordinary molecular
diversity within the preBötC and demonstrated that small numbers of molecularly distinct preBötC cell types
have highly specific functions in the breathing behavior. I am poised to continue this dissection with the
objective of identifying the core neurons that initiate a breath and control the pace of breathing.