Related Experiment Video
Updated: Jun 7, 2025
07:32
Biolistic Transformation of a Fluorescent Tagged Gene into the Opportunistic Fungal Pathogen Cryptococcus neoformans
Published on: March 19, 2015
9.9K
Distinct evolutionary trajectories following loss of RNA interference in Cryptococcus neoformans
Jun Huang1, Connor J Larmore1, Shelby J Priest1
1Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710.
Summary
Loss of RNA interference (RNAi) in microbes like Cryptococcus neoformans can enable rapid adaptation. This study reveals RNAi loss is common and can lead to hypermutation and drug resistance through transposon activity or allow survival without it.
Area of Science:
- Microbiology
- Evolutionary Biology
- Genetics
Background:
- Hypermutation, while detrimental in multicellular organisms, can drive microbial adaptation.
- Previous work identified hypermutator Cryptococcus neoformans strains with drug resistance linked to retrotransposon Cnl1, caused by ZNF3 gene mutations and high transposon load.
- RNA interference (RNAi) is crucial for genome stability and regulating transposons.
Purpose of the Study:
- To investigate adaptive mechanisms and evolutionary trajectories following RNA interference (RNAi) loss in Cryptococcus neoformans.
- To identify and characterize RNAi loss-of-function (LOF) mutations in a large isolate collection.
- To determine if RNAi loss alone or in combination with transposon accumulation drives hypermutation.
Main Methods:
- Developed two bioinformatic pipelines to detect RNAi LOF mutations in 387 C. neoformans isolates.
- Introduced identified RNAi LOF mutations into a non-hypermutator strain to assess their effect on mutation rate.
- Performed in vitro passaging of RNAi-loss strains and genetic crosses to study hypermutation evolution.
Main Results:
- Identified RNAi LOF mutations in 7 out of 387 (approx. 1.8%) C. neoformans isolates; several were not hypermutators.
- Experimental introduction of RNAi LOF mutations into a high-transposon-burden strain induced a hypermutator phenotype.
- In vitro passaging showed hypermutation in Cryptococcus deneoformans but not C. neoformans, while genetic crosses yielded hypermutator progeny with high burdens of Cnl1 and KDZ1 transposons.
Conclusions:
- RNAi loss is a frequent event in C. neoformans, providing distinct evolutionary pathways.
- RNAi loss can predispose microbes to hypermutation and rapid adaptation, particularly when coupled with transposon activity.
- These findings highlight the dual role of RNAi loss in microbial evolution: enabling adaptation via hypermutation or facilitating survival through other mechanisms.
Related Concept Videos
01:23Cystic Fibrosis: Pathogenesis
192
Cystic fibrosis (CF), an autosomal recessive disorder, significantly affects the function of exocrine glands. This genetically inherited disease is characterized by the production of thick and sticky mucus, which can severely affect various organs and systems in the body.
CF is primarily caused by a genetic mutation in a chromosome 7 gene coding for the cystic fibrosis transmembrane conductance regulator (CFTR) protein. The most common gene mutation leading to CF is the ΔF508 mutation,...
CF is primarily caused by a genetic mutation in a chromosome 7 gene coding for the cystic fibrosis transmembrane conductance regulator (CFTR) protein. The most common gene mutation leading to CF is the ΔF508 mutation,...
192
01:10Retrovirus Life Cycles
45.7K
Retroviruses have a single-stranded RNA genome that undergoes a special form of replication. Once the retrovirus has entered the host cell, an enzyme called reverse transcriptase synthesizes double-stranded DNA from the retroviral RNA genome. This DNA copy of the genome is then integrated into the host’s genome inside the nucleus via an enzyme called integrase. Consequently, the retroviral genome is transcribed into RNA whenever the host’s genome is transcribed, allowing the...
45.7K
01:29Viruses with RNA Genomes
3
RNA viruses are categorized into positive-strand, negative-strand, or double-stranded groups based on their genomic structure and replication mechanisms. This classification dictates how they exploit host cellular machinery for protein synthesis and replication. Some RNA viruses also utilize reverse transcription as part of their life cycle, further diversifying their replication strategies.Positive-Strand RNA VirusesPositive-strand RNA viruses have genomes that function directly as messenger...
3
02:15Experimental RNAi
6.1K
RNA interference (RNAi) is a cellular mechanism that inhibits gene expression by suppressing its transcription or activating the RNA degradation process. The mechanism was discovered by Andrew Fire and Craig Mello in 1998 in plants. Today, it is observed in almost all eukaryotes, including protozoa, flies, nematodes, insects, parasites, and mammals. This precise cellular mechanism of gene silencing has been developed into a technique that provides an efficient way to identify and determine the...
6.1K
00:36Viral Mutations
32.2K
A mutation is a change in the sequence of bases of DNA or RNA in a genome. Some mutations occur during replication of the genome due to errors made by the polymerase enzymes that replicate DNA or RNA. Unlike DNA polymerase, RNA polymerase is prone to errors because it is not capable of “proofreading” its work. Viruses with RNA-based genomes, like HIV, therefore accrue mutations faster than viruses with DNA-based genomes. Because mutation and recombination provide the raw material...
32.2K
01:12Loss of Tumor Suppressor Gene Functions
4.7K
Tumor suppressor genes are normal genes that can slow down cell division, repair DNA mistakes, or program the cells for apoptosis in case of irreparable damage. Hence, they play an essential role in preventing the proliferation of damaged cells.
When the tumor suppressor genes develop mutations or are lost, cells start growing out of control, leading to cancer. However, a single functional copy of the tumor suppressor gene is enough for the cells to maintain their normal functions and cell...
When the tumor suppressor genes develop mutations or are lost, cells start growing out of control, leading to cancer. However, a single functional copy of the tumor suppressor gene is enough for the cells to maintain their normal functions and cell...
4.7K