# Impact of RNAi and unisexual reproduction on Cryptococcus evolution, drug resistance, and pathogenesis

> **NIH NIH R01** · DUKE UNIVERSITY · 2021 · $642,774

## Abstract

Abstract
 Cryptococcus neoformans and Cryptococcus gattii are globally distributed fungal pathogens that cause
>220,000 life-threatening infections each year in immunocompromised and immunocompetent patients, leading
to >180,000 deaths, >15% of all HIV/AIDS-related deaths, and >70% mortality in low-income countries. In studies
supported by this award, the scope and functions of a- and - sexual reproduction on the evolution and
pathogenesis of Cryptococcus were defined. Sexual reproduction governs population structure, enabling genetic
exchange and promoting clonality, and results in the production of infectious spores.
 During this sustained funding period, significant advances were achieved characterizing the mechanisms
and impact of sexual reproduction on these pathogens and their virulence: 1) discovery of roles of RNAi in
controlling transposon movement and transgene silencing during mitosis and meiosis and characterization of
the consequences of RNAi loss on genome structure and stability; 2) studies on generation and affect of
aneuploidy on drug resistance, pathogenicity, and development, and engineering of a ploidy sensor to analyze
genetic factors contributing to endoreplication during unisexual reproduction; 3) delineation of isolates causing
the C. gattii outbreak in the Pacific Northwest and closely aligned hypermutator lineages, and 4) demonstration
that unisexual reproduction generates genetic diversity de novo and enhances competitiveness for nutrients and
mating partners. In the current proposal, we hypothesize 1) RNAi has been retained and lost in unique isolates
and species, influencing genomic stability and driving evolution of drug resistance and pathogenesis, and 2)
unisexual reproduction is a major force in evolution, global distribution, and impact of Cryptococcus pathogens.
 Our studies reveal unique facets of RNAi and sexual reproduction enabling us to propose new aims to test
these hypotheses. Aim 1 focuses on RNAi in genome stability, elucidating components and mechanisms by
which RNAi controls transposons and silences repetitive DNA sequences, and studying the short-term and long-
term consequences of RNAi loss on drug resistance and pathogenesis in C. neoformans hypermutator clinical
isolates and the RNAi-deficient C. deuterogattii outbreak species. Aim 2 will elucidate unisexual reproduction
pathways and mechanisms involving 1) unisexual reproduction occurring in mixed mating-type populations
and in strains with rearranged genomes as a model of speciation, 2) genetic and environmental factors that
promote unisexual reproduction of global serotype A lineages and analysis of infectious spores in animal models,
and 3) overcoming the Hill-Robertson effect to enable linkage of beneficial mutations and separation of
detrimental and beneficial mutations to enhance fitness and pathogenesis. These studies will advance the
understanding of how genome stability and unisexual reproduction drive pathogen evolution and populatio...

## Key facts

- **NIH application ID:** 10117352
- **Project number:** 2R01AI039115-24
- **Recipient organization:** DUKE UNIVERSITY
- **Principal Investigator:** JOSEPH HEITMAN
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $642,774
- **Award type:** 2
- **Project period:** 1997-05-01 → 2026-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10117352

## Citation

> US National Institutes of Health, RePORTER application 10117352, Impact of RNAi and unisexual reproduction on Cryptococcus evolution, drug resistance, and pathogenesis (2R01AI039115-24). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10117352. Licensed CC0.

---

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