Related Experiment Video
Updated: Aug 10, 2026
09:57
siRNA Transfection and EMSA Analyses on Freshly Isolated Human Villous Cytotrophoblasts
Published on: September 20, 2016
Placenta-specific INSL4 expression is mediated by a human endogenous retrovirus element
Ivan Bièche1, Anne Laurent, Ingrid Laurendeau
1Laboratoire de Génétique Moléculaire, Faculté des Sciences Pharmaceutiques et Biologiques, Univeristé René Descartes, Paris, France.
Biology of Reproduction
|February 28, 2003
Summary
Ancient retroviral elements integrated into the human INSL4 gene promoter drive its placenta-specific expression, highlighting retroviral impact on primate evolution and placental function.
Area of Science:
- Genomics
- Evolutionary Biology
- Reproductive Biology
Background:
- Human insulin-family genes regulate vital cellular processes.
- INSL4 is unique among these for its placenta-specific expression.
- The INSL4 gene's evolutionary origins and regulatory mechanisms are largely unknown.
Purpose of the Study:
- To investigate the genomic organization and evolutionary history of the human INSL4 gene.
- To elucidate the regulatory elements controlling INSL4's placenta-specific expression.
- To explore the role of endogenous retroviruses in INSL4 gene regulation and primate evolution.
Main Methods:
- Comparative genomics to analyze gene clustering and primate-specificity.
- Identification and characterization of inserted elements within the INSL4 promoter region.
- Transient transfection assays to assess the functional role of HERV elements in gene expression.
- Analysis of INSL4 mRNA splicing variants.
Main Results:
- The human INSL4 gene is clustered with other insulin superfamily members on chromosome 9p23.3-p24.1.
- INSL4 appears to be primate-specific, with its emergence and HERV insertion post-monkey divergence.
- A human endogenous retrovirus (HERV) element within the INSL4 promoter, specifically its 3' LTR, mediates placenta-specific expression and up-regulation.
- An alternatively spliced INSL4 mRNA encoding novel peptides was identified.
Conclusions:
- Ancient retroviral elements have significantly influenced the functional evolution of the human placenta.
- The HERV insertion in the INSL4 promoter is crucial for its placental expression, suggesting retroviral domestication.
- This finding underscores the substantial role of endogenous retroviruses in shaping primate genomes and reproductive biology.
Related Concept Videos
01:10Retrovirus Life Cycles
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 retrovirus to...
02:33Retroviruses
Retroviruses and retrotransposons both insert copies of their genetic elements into the genome of the host cell. Thus, the viral genes are passed on when the host genome is replicated or translated. A typical retroviral DNA sequence contains 3-4 genes that encode the different proteins required for its structural assembly and function as a molecular parasite. This DNA is transcribed into a single mRNA, which is very similar in structure to conventional mRNAs, i.e., it is capped at the 5’...
03:08LTR Retrotransposons
LTR retrotransposons are class I transposable elements with long terminal repeats flanking an internal coding region. These elements are less abundant in mammals compared to other class I transposable elements. About 8 percent of human genomic DNA comprises LTR retrotransposons. Some of the common examples of LTR retrotransposons are Ty elements in yeast and Copia elements in Drosophila.
The internal coding region of LTR retrotransposons and their mechanism of transposition closely resembles a...
The internal coding region of LTR retrotransposons and their mechanism of transposition closely resembles a...
03:18Non-LTR Retrotransposons
As the name suggests, non-LTR retrotransposons lack the long terminal repeats characteristic of the LTR retrotransposons. Additionally, both LTR and non-LTR retrotransposons use distinct mechanisms of mobilization. Non-LTR retrotransposons are further divided into two classes - Long interspersed nuclear elements (LINEs) and short interspersed nuclear elements (SINEs), both of which occur abundantly in most mammals, including humans. Some of the active non-LTR retrotransposons in humans are L1...
02:57piRNA - Piwi-interacting RNAs
PIWI-interacting RNAs, or piRNAs, are the most abundant short non-coding RNAs. More than 20,000 genes have been found in humans that code for piRNAs while only 2000 genes have been found for miRNAs. piRNAs can act at the transcriptional and post-transcriptional levels and have a vital role in silencing transposable elements present in germ cells. They are also involved in epigenetic silencing and activation. Previously, they were thought to function only in germ cells but new evidence suggests...