Small interfering RNA biology

Small RNA-mediated regulation of gene expression is believed to contribute to essentially all genetic pathways in animals, yet detailed biological examples are few in number. MicroRNAs (miRNAs), the best understood class of small RNAs, are non-coding, regulatory RNAs that post-transcriptionally repress gene expression by targeting specific mRNAs for repression. The importance of miRNAs is well illustrated by mouse models: many miRNA loss-of-function or overexpression lines exhibit overt phenotypes, including developmental defects, lethality and susceptibility to disease, including cancers. However, few studies have defined the specific mRNAs targeted by miRNAs in normal mouse or human developmental pathways. In addition to miRNAs, there are other classes of related small RNAs, including endogenous siRNAs (short-interfering RNAs) and piRNAs (piwi-interacting RNAs); the different classes of small RNAs employ a diversity of mechanisms, but all function to regulate gene expression. Several studies have suggested that germline development and function require small RNAs, implicating roles for miRNAs, siRNAs and piRNAs in the germline. Studies by members of the Cornell CRG are directed towards understanding the relative roles of these small RNA species in the germline and extrapolating these functions throughout the reproductive system. Our projects include:

1. Defining the regulatory functions of small RNAs in male germ cells of the mouse, led by Dr. Andrew Grimson.

2. Role of small RNAs in human male infertility, led by Darius Paduch and Peter Schlegel

3. Elucidating the roles of mammalian Argonautes (AGO3 & 4) in meiotic prophase I, led by Paula Cohen

PILOT: CRISPR-mediated mutagenesis of microRNA clusters in the mouse, led by John Schimenti.

 

Figure 1. Localization of microRNAs (red) to the XY body in prophase I spermatocytes from wildtype (WT) and Ago4 mutant males. From Paula E. Cohen and Andrew Modzelewski.

Copyright Paula E. Cohen, 2015

 

Research Areas

A. Small RNA biology

B. Klinefelter Syndrome

C. Mammalian meiosis

D. Germline genome integrity

CRG News

Grimson and Cohen Labs identify critical regulatory pathways involving non-coding RNAs in sex body integrity during meiosis

A new study from Andrew Grimson's lab, in collaboration with Paula Cohen's lab, has identified a key pathway required for maintenance of sex chromosome telomere integrity. Using conditional knockout mice for Dicer and Dgcr8, two key enzymes required for small RNA processing, Modzelewski et al (2015) show that loss of small RNAs during prophase I leads to telomere fusion events specifically involving the X and Y chromosomes. For further information, see the May edition of Journal of Cell Science

Paduch Lab identifies critical Sertoli Cell-Germ cell interactions in human testis

A recent publication by Dabaja et al (2015) has identified key cell:cell interactions that are necessary to establish normal profiles of one key microRNA, miR202-5p, in Sertoli cells. This is the first example of a germ cell regulatory interaction that is necessary for miR expression in neighboring somatic cells of the testis

Six Postdoctoral Fellows awarded CRG seed grants
Six outstanding postdoctoral fellows have been awarded seed grants of between $5000 and $10,000 to initiate studies of non-coding RNAs in reproduction. All six projects have a firmly translational basis, and range from identification of long non-coding RNAs in meiosis, to establishing mechanisms by which small non-coding RNAs regulate estrogen production in the ovary. Funds will support experimental studies and use of the RNA Sequencing Core for up to one year.
Annual CRG symposium attracts researchers from over 15 institutions to Ithaca!
The CRG Annual Symposium was held in April, 2016, concurrent with the meeting of the NICHD Male Research Focus Group Meeting on the Ithaca campus of Cornell University. Over 150 participants from two Cornell campuses, along with guests from across the country, and researchers from neighboring institutions assembled together for this 2-day event. Prizes were awarded for the best trainee poster and oral presentation. For photos and coverage, click here.
Schimenti Lab sheds light on DNA damage checkpoint regulation in mammalian oocytes

The lab of Center member John Schimenti  recently identified the DNA damage checkpoint pathway responsible for culling oocytes that fail to repair double stranded breaks (DSBs) that occur during meiosis or which arise in a female's oocyte pool (Bolcun-Filas et al, Science 343:533-536, 2014).  Using combinations of mutants involved in recombination and DNA damage responses, they found that this pathway involves signaling of checkpoint kinase 2 (CHK2) to both p53 and p63. Disruption of this checkpoint pathway restored fertility to females that normally would be deficient of all oocytes due to defects in meiotic recombination or exposure to radiation. This discovery opens the way to using available CHK2 inhibitors to protect the oocytes of women undergoing cancer therapy that would normally cause infertility.