Jeannie T. Lee | |
---|---|
Alma mater | Harvard University, University of Pennsylvania Medical School, Massachusetts Institute of Technology |
Awards | 2018 Harrington Rare Genetic Disease Scholar 2016 Lurie Award 2016 Centennial Award from Genetics Society of America 2015 Election to National Academy of Sciences (NAS) 2010 Molecular Biology Award from NAS 1999 Pew Scholar 1998 Basil O'Connor ScholarContents |
Scientific career | |
Fields | epigenetics, long noncoding RNA, X-inactivation, 3D genome, X-chromosome reactivation technology |
Thesis | (1993) |
Academic advisors | Nancy Kleckner, Robert Nussbaum, Rudolf Jaenisch |
Jeannie T. Lee is a Professor of Genetics (and Pathology) at Harvard Medical School and the Massachusetts General Hospital, and a Howard Hughes Medical Institute Investigator. She is known for her work on X-chromosome inactivation and for discovering the functions of a new class of epigenetic regulators known as long noncoding RNAs (lncRNAs), including Xist and Tsix.
Jeannie T. Lee received an AB from Harvard College in Biochemistry & Molecular Biology and an MD/PhD in 1993 [1] from the University of Pennsylvania School of Medicine. [2] While at Harvard she worked with Nancy Kleckner on antisense regulation of Tn10 transposition. While at University of Pennsylvania School of Medicine her advisor was Robert L. Nussbaum. [3] Her PhD research focused on Fragile X syndrome, and led to her strong interest in X chromosome inactivation and epigenetics. [4] Then she did postdoctoral work with Rudolf Jaenisch at the Whitehead Institute , during which she discovered the nature of the X-inactivation center. [3] She was also Chief Resident of Laboratory Medicine at the Massachusetts General Hospital.
Lee joined the faculty at Harvard in 1997 and devoted her studies to noncoding RNA and sex chromosome dynamics during development and disease. Her major career research achievements include identifying the X inactivation center, [5] [6] discovering Tsix antisense RNA, [7] determining Xist's mechanism of action, [8] [9] demonstrating that a lncRNA is a regulator of Polycomb repressive complex 2, [8] [10] [11] [12] and determining that the X chromosome folds like origami and adopts a unique conformation.
Her studies established the existence and function of a group of lncRNAs. In a 2013 interview, she stated that this group of RNAs excited her because they control gene expression in a locus-specific way, by recruiting chromatin modifying activities to the locus, making the lncRNAs excellent drug design targets. She founded RaNA Therapeutics to test this idea. [3]
Upon conferring the Lurie Prize to Lee in 2016, Dr. Charles A. Sanders of the Foundation for the National Institutes of Health remarked: “Dr. Lee’s work has revolutionized the field of epigenetics. Her research has led to groundbreaking contributions, and we now have a better understanding of the unique role that long non-coding RNAs play in gene expression, which could lead to the development of new therapeutics.” [13]
Lee was President of the Genetics Society of America, [14] Codirector of the Harvard Epigenetics Initiative, and is Vice Chair of the Department of Molecular Biology, Massachusetts General Hospital, Harvard Medical School. She delivered a set of lectures to iBiology on X chromosome inactivation. [15]
A Barr body or X-chromatin is an inactive X chromosome. In species with XY sex-determination, females typically have two X chromosomes, and one is rendered inactive in a process called lyonization. Errors in chromosome separation can also result in male and female individuals with extra X chromosomes. The Lyon hypothesis states that in cells with multiple X chromosomes, all but one are inactivated early in embryonic development in mammals. The X chromosomes that become inactivated are chosen randomly, except in marsupials and in some extra-embryonic tissues of some placental mammals, in which the X chromosome from the sperm is always deactivated.
Peptide nucleic acid (PNA) is an artificially synthesized polymer similar to DNA or RNA.
A non-coding RNA (ncRNA) is a functional RNA molecule that is not translated into a protein. The DNA sequence from which a functional non-coding RNA is transcribed is often called an RNA gene. Abundant and functionally important types of non-coding RNAs include transfer RNAs (tRNAs) and ribosomal RNAs (rRNAs), as well as small RNAs such as microRNAs, siRNAs, piRNAs, snoRNAs, snRNAs, exRNAs, scaRNAs and the long ncRNAs such as Xist and HOTAIR.
Antisense RNA (asRNA), also referred to as antisense transcript, natural antisense transcript (NAT) or antisense oligonucleotide, is a single stranded RNA that is complementary to a protein coding messenger RNA (mRNA) with which it hybridizes, and thereby blocks its translation into protein. The asRNAs have been found in both prokaryotes and eukaryotes, and can be classified into short and long non-coding RNAs (ncRNAs). The primary function of asRNA is regulating gene expression. asRNAs may also be produced synthetically and have found wide spread use as research tools for gene knockdown. They may also have therapeutic applications.
Dosage compensation is the process by which organisms equalize the expression of genes between members of different biological sexes. Across species, different sexes are often characterized by different types and numbers of sex chromosomes. In order to neutralize the large difference in gene dosage produced by differing numbers of sex chromosomes among the sexes, various evolutionary branches have acquired various methods to equalize gene expression among the sexes. Because sex chromosomes contain different numbers of genes, different species of organisms have developed different mechanisms to cope with this inequality. Replicating the actual gene is impossible; thus organisms instead equalize the expression from each gene. For example, in humans, female (XX) cells randomly silence the transcription of one X chromosome, and transcribe all information from the other, expressed X chromosome. Thus, human females have the same number of expressed X-linked genes per cell as do human males (XY), both sexes having essentially one X chromosome per cell, from which to transcribe and express genes.
X-inactivation is a process by which one of the copies of the X chromosome is inactivated in therian female mammals. The inactive X chromosome is silenced by being packaged into a transcriptionally inactive structure called heterochromatin. As nearly all female mammals have two X chromosomes, X-inactivation prevents them from having twice as many X chromosome gene products as males, who only possess a single copy of the X chromosome.
Polycomb-group proteins are a family of protein complexes first discovered in fruit flies that can remodel chromatin such that epigenetic silencing of genes takes place. Polycomb-group proteins are well known for silencing Hox genes through modulation of chromatin structure during embryonic development in fruit flies. They derive their name from the fact that the first sign of a decrease in PcG function is often a homeotic transformation of posterior legs towards anterior legs, which have a characteristic comb-like set of bristles.
KCNQ1 overlapping transcript 1, also known as KCNQ1OT1, is a long non-coding RNA gene found in the KCNQ1 locus. This locus consists of 8–10 protein-coding genes, specifically expressed from the maternal allele, and the paternally expressed non-coding RNA gene KCNQ1OT1. KCNQ1OT1 and KCNQ1 are imprinted genes and are part of an imprinting control region (ICR). Mitsuya identified that KCNQ1OT1 is an antisense transcript of KCNQ1. KCNQ1OT1 is a paternally expressed allele and KCNQ1 is a maternally expressed allele. KCNQ1OT1 is a nuclear, 91 kb transcript, found in close proximity to the nucleolus in certain cell types.
Xist is a non-coding RNA transcribed from the X chromosome of the placental mammals that acts as a major effector of the X-inactivation process. It is a component of the Xic – X-chromosome inactivation centre – along with two other RNA genes and two protein genes.
Long non-coding RNAs are a type of RNA, generally defined as transcripts more than 200 nucleotides that are not translated into protein. This arbitrary limit distinguishes long ncRNAs from small non-coding RNAs, such as microRNAs (miRNAs), small interfering RNAs (siRNAs), Piwi-interacting RNAs (piRNAs), small nucleolar RNAs (snoRNAs), and other short RNAs. Given that some lncRNAs have been reported to have the potential to encode small proteins or micro-peptides, the latest definition of lncRNA is a class of RNA molecules of over 200 nucleotides that have no or limited coding capacity. Long intervening/intergenic noncoding RNAs (lincRNAs) are sequences of lncRNA which do not overlap protein-coding genes.
HOTAIR is a human gene located between HOXC11 and HOXC12 on chromosome 12. It is the first example of an RNA expressed on one chromosome that has been found to influence transcription of HOXD cluster posterior genes located on chromosome 2. The sequence and function of HOTAIR is different in human and mouse. Sequence analysis of HOTAIR revealed that it exists in mammals, has poorly conserved sequences and considerably conserved structures, and has evolved faster than nearby HoxC genes. A subsequent study identified HOTAIR has 32 nucleotide long conserved noncoding element (CNE) that has a paralogous copy in HOXD cluster region, suggesting that the HOTAIR conserved sequences predates whole genome duplication events at the root of vertebrate. While the conserved sequence paralogous with HOXD cluster is 32 nucleotide long, the HOTAIR sequence conserved from human to fish is about 200 nucleotide long and is marked by active enhancer features.
In molecular biology, JPX transcript, XIST activator, also known as Jpx, is a long non-coding RNA. In humans, it is located on the X chromosome. It was identified during sequence analysis of the X inactivation centre, surrounding the Xist gene. Jpx upregulates expression of Xist.
HOXA11-AS lncRNA is a long non-coding RNA from the antisense strand in the homeobox A. The HOX gene contains four clusters. The sense strand of the HOXA gene codes for proteins. Alternative names for HOXA11-AS lncRNA are: HOXA-AS5, HOXA11S, HOXA11-AS1, HOXA11AS, or NCRNA00076. This gene is 3,885 nucleotides long and resides at chromosome 7 (7p15.2) and is transcribed from an independent gene promoter. Being a lncRNA, it is longer than 200 nucleotides in length, in contrast to regular non-coding RNAs.
Tsix is a non-coding RNA gene that is antisense to the Xist RNA. Tsix binds Xist during X chromosome inactivation. The name Tsix comes from the reverse of Xist, which stands for X-inactive specific transcript.
Epigenetics of human development is the study of how epigenetics effects human development.
X chromosome inactivation (XCI) is the phenomenon that has been selected during the evolution to balance X-linked gene dosage between XX females and XY males.
Neil Alexander Steven Brockdorff is a Wellcome Trust Principal Research Fellow and professor in the department of biochemistry at the University of Oxford. Brockdorff's research investigates gene and genome regulation in mammalian development. His interests are in the molecular basis of X-inactivation, the process that evolved in mammals to equalise X chromosome gene expression levels in XX females relative to XY males.
Carolyn J. Brown is a Canadian geneticist and Professor in the Department of Medical Genetics at the University of British Columbia. Brown is known for her studies on X-chromosome inactivation, having discovered the human XIST gene in 1990.
A majority of the human genome is made up of non-protein coding DNA. It infers that such sequences are not commonly employed to encode for a protein. However, even though these regions do not code for protein, they have other functions and carry necessary regulatory information.They can be classified based on the size of the ncRNA. Small noncoding RNA is usually categorized as being under 200 bp in length, whereas long noncoding RNA is greater than 200bp. In addition, they can be categorized by their function within the cell; Infrastructural and Regulatory ncRNAs. Infrastructural ncRNAs seem to have a housekeeping role in translation and splicing and include species such as rRNA, tRNA, snRNA.Regulatory ncRNAs are involved in the modification of other RNAs.
X chromosome reactivation (XCR) is the process by which the inactive X chromosome (the Xi) is re-activated in the cells of eutherian female mammals. Therian female mammalian cells have two X chromosomes, while males have only one, requiring X-chromosome inactivation (XCI) for sex-chromosome dosage compensation. In eutherians, XCI is the random inactivation of one of the X chromosomes, silencing its expression. Much of the scientific knowledge currently known about XCR comes from research limited to mouse models or stem cells.