# Building Dendrite Architecture via Microtubule Nucleation

> **NIH NIH K99** · PRINCETON UNIVERSITY · 2024 · $125,000

## Abstract

Microtubules (MTs) are a major component of the eukaryotic cytoskeleton, and their formation and activity are a
primary driver of cellular architecture. MT formation in the cell requires the presence of a universal MT nucleation
module, made up of the γ-tubulin ring complex (γ-TuRC), which acts as a template for tubulin assembly into MTs,
and its co-nucleator, XMAP215. The formation of specialized MT-based structures relies on biochemical
pathways that recruit and activate γ-TuRC at specific sites. Previously, it was thought that all MTs originated from
centrosomes. However, we now know that this is not correct and that there are numerous other MT organizing
centers (MTOCs). The mitotic spindle is an excellent example of MT assembly, and will be the focus of Aim 1 in
the proposed K99. In acentrosomal spindles, chromosomes act as the primary drivers of MT nucleation through
a gradient of activated RanGTP. Downstream of Ran, the augmin complex recruits γ-TuRC to form new MTs from
pre-existing ones in a pathway called branching MT nucleation. Branching MT nucleation amplifies MT mass
while conserving polarity and we now know that branching MT nucleation is responsible for generating the bulk
of MTs in the spindle. The pressing question driving K99 Aim 1 is how, precisely, does a spindle emerge from
branched MT networks? In this aim, I will use in vitro reconstitution to determine how branched MTs undergo
nucleation near chromosomes during early spindle assembly, and how these branched networks mature into a
spindle. My research will elucidate how single MTs that are a mere 25 nm in diameter self-organize into a micron-
scale structure that performs essential functions of the cell. Then, in Aim 2 of the K99, I will uncover which spindle
assembly factors are used to build other MT-based structures. Specifically, I will perform a targeted RNAi screen
using Drosophila dendritic arborization (da) neurons, which display highly elaborate patterning, as a model
system to determine which acentrosomal MT nucleation effectors have a role in dendrite formation. Finally, in
the R00 phase of my research, I will determine how MTs are nucleated in dendrites throughout development,
and how this nucleation contributes to dendrite patterning observed in mature neurons. To do this, in R00 Aim 1,
I will use super-resolution imaging to precisely quantify where MTOCs appear in dendrites and explore how
MTOCs execute MT nucleation using acentrosomal pathways. In Aim 2 of the R00 section, I will perform proximity
labeling and use expansion microscopy with super-resolution imaging to define the nanoscale protein
architecture of dendritic MTOCs, yielding key insights about the role of MT nucleation in driving dendrite
morphogenesis, which ultimately gives rise to neuronal function. Each phase of my research will prepare me to
run an independent research lab, with the goal of using my skills to substantially advance understanding of
cellular architecture and how architecture b...

## Key facts

- **NIH application ID:** 11032466
- **Project number:** 1K99GM157463-01
- **Recipient organization:** PRINCETON UNIVERSITY
- **Principal Investigator:** JODI KRAUS
- **Activity code:** K99 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $125,000
- **Award type:** 1
- **Project period:** 2024-09-10 → 2026-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/11032466

## Citation

> US National Institutes of Health, RePORTER application 11032466, Building Dendrite Architecture via Microtubule Nucleation (1K99GM157463-01). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/11032466. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*