ELABELA (abbreviated ELA) is a secreted hormonal peptide
acting during embryogenesis and circulating in blood in the adult.
Genomic
The ELABELA gene is located on chromosome 4q32.3 in humans.
It consists of 3 exons with the following genomic coordinates
(hg19): chr4:165,798,156-165,818,675 .
Exon 1 codes for all the 5’ UTR, the entire signal peptide
and 3 residues of the mature peptide.
Exon 2 encodes the mature ELA peptide and its Stop codon.
Exon 3, which is the largest of all, is entirely consisting of
3’ UTR. In primates but not in rodents, the exon 3 is larger and
bears 2 Alu repeats of 300 bp each.
1 MRFQQFLFAFFIFIMSLLLISGQRPVNLTMRRKLRKHNCLQRRCMPLHSRVPFP 54
1 Exon 1 V Exon
2 54
The GTT codon for Valine is overlapping splice sites between
exon 1 and exon 2.
The open reading frame (ORF) encoded by the human ELA
cDNA is 165 bp in length:
>human ELABELA ORF
ATGAGATTTCAGCAATTCCTTTTTGCATTTTTTATTTTTATTAT
GAGTCTTCTCCTTATCAGCGGACAGAGACCAGTTAATTTGACC
ATGAGAAGAAAACTGCGCAAACACAATTGCCTTCAGAGGAGA
TGTATGCCTCTCCATTCACGAGTACCCTTTCCCTGA
ELABELA is a novel peptide hormone that was identified,
characterized and de-orphaned in 2013 by the team of
Dr. Bruno REVERSADE at the Institute of Medical Biology
in Singapore.
It's name stands for Epiboly LAte Because of Endoderm LAte
(or vice versa) which is the first observable phenotype when
knocked out in zebrafish.
Biosynthesis
The human ELABELA gene encodes a protein of 54 amino-acids,
with a signal peptide in its N-terminal region.
It is referenced in Uniprot under PODMC3.
After cleavage of the signal peptide which consists of the
first 22 residues, the mature ELA hormone is 32 amino-acid
long with an isoelectric point exceeding 12.
ELA needs to be secreted to become active since deletion
of 7 residues in its signal peptide causes a complete
loss-of-function in zebrafish.
Mature ELA bears 2 conserved di-arginine motifs
(R31/R32 and R42/R43) suggesting that it may be further processed
by Furin-like endopeptidase. It is beleived that the N-terminal residue
of the mature peptide can be substituted by a pyroglutamic acid (Pyr)
residue as is the case in APLN-13.
ELABELA |
Primary Sequence |
Molecular Weight (Da) |
Isoelectric |
full-length peptide |
MRFQQFLFAFFIFIMSLLLISGQRPVNLTMRRKLRKHNCLQRRCMPLHSRVPFP |
6622 |
12.2 |
signal peptide |
MRFQQFLFAFFIFIMSLLLISG |
2670 |
9.50 |
mature peptide |
QRPVNLTMRRKLRKHNCLQRRCMPLHSRVPFP |
3970 |
12.1 |
Antibodies
The full-length and mature endogenou ELA peptide can be
recognized by a mouse monoclonal or rabbit polyclonal antibody
raised against this C-terminal 11-mer epitope CMPLHSRVPFP.
These antibodies referred to as "anti-C" can recognize ELA from
any species and have strong neutralizing activity towards
ELA' s activity in hESCs.
The mature endogenous human ELA peptide can be
recognized by a mouse monoclonal or rabbit polyclonal antibody
raised against the N-terminal 17-mer epitope
QRPVNLTMRRKLRKHNC. These antibodies referred to as "anti-N"
have strong neutralizing activity towards ELA' s activity in hESCs.
Phylogeny
The ELABELA protein is phylogenetically conserved across
all vertebrate species with an invariable length of 54 amino acids.
species |
primary
amino-acid sequence |
Homo Peromyscus Rattus Mus Bos Sus Dasypus Trichosurus Gallus Gekko Anolis Xenopus Ambystoma |
1 10 23 30 40 50 54 |
However, in zebrafish (Danio rerio), Ela has an additional
4 amino-acids. This insertion of 4 residues (DKHG) is predicted
to be part of the mature peptide:
1-MRFFHPLYLLLLLLTVLVLISA(DKHG)TKHDFLNLRRKYRRHNCPKKRCLPLHSRVPFP-58
Its carboxy terminal end is invariant across species and
comprises the signature: -HSRVPFPstop
ELA also contains a pair of conserved cysteines residues at
position 39 and 44 that form an intermolecular disulphide bridge.
A mutant form of ELA with two carboxy missense mutations
(p.F53A; p.P54A) is believed to act as an antagonist to APLNR.
A mutant form of ELA with two N-terminal missense mutations
(p.R31G; p.R32G) can no longer bind to the cell surface of
hESCs which express ELA' s alternate receptor.
Two Receptors
ELA is the earliest known endogenous ligand
for the cell surface G protein-coupled receptor APLNR
(also known as APJ and AGTRL1).
The other known ligand for APLNR is the hormonal peptide
APELIN. Both ligands have similar binding kinetics to APLNR
and can compete for one another suggesting similar binding
sites to this GPCR.
ELA possesses a second cell surface receptor in hESCs
which signals via the PI3K/AKT signalling pathway to mediate
hESCs self-renewal. The identity of this second receptor is
yet unknown.
ELABELA is expressed in naive cells of the ectoderm or epiblast
and signals to the future endodermal cells expressing APLNR.
In zebrafish embryos, ELABELA is needed for proper gata5 and
sox17 expression during gastrulation.
ELABELA regulates the migration of cell progenitors fated to
differentiate in cardiac tissue.
ELABELA has been proposed to act as a motogen to promote
cell motility during epiboly and as a classical chemo-attractant
for the migration of angioblasts to the embryonic midline.
elabela knockout zebrafish have rudimentary heart or not heart
at all. In addition Ela mutant larvae show excess red blood cells
in the intermediate cell mass, no blood circulation,
and variable posterior truncations as do double zebrafish
aplnra;aplnrb mutants.
Heart morphogenesis in aplnra;aplnrb double knockout fish can be
partially rescued by elevating Nodal/TGFbeta signalling.
Vascular
In zebrafish, the double ligand knockout of elabela;apelin , which
are expressed at the embryonic midline,impedes migration
of angioblasts to form the primary vessels namely the aorta and
the cardinal vein. This process known as vasculogenesis is
mediated by Aplnra and Aplnrb which are expressed at the cell
surface of angioblasts.
In mouse, Elabela is needed for proper yolk sac vasculature and
placental angiogenesis. Its mutation phenocopies that of Aplnr.
Pregnant mice lacking Ela, but not Apelin, develop symptoms of pre-
-eclampsia with gestational hypertension, proteinuria and IUGR.
This symptoms can be rescued by infusing ELA indicating that the
ELABELA-nergic may be of therapeutic value in hypertensive syndromes.
Pre-eclampsia
The sFas/Fas system and Elabela-APLNR signaling pathways are implicated
in the pathophysiology of preeclampsia. A combined model of maternal sFas
and ELABELA concentrations provides a stronger association with late-onset
preeclampsia than either protein alone. This demonstrates the possibility to
improve the classification of late-onset preeclampsia by combining the results
of both circulating molecular biomarkers.
The endogenous levels of circulating ELABELA in women with late-onset pre-
eclampsia (8.0 ng/mL), but not early onset preeclampsia, was found to be
higher than in normotensive gestational-age-matched pregnancies (4.2 ng/mL).
Essential Hypertension
ELABELA has a critical role in eliciting vasodilation and lowering blood
pressure. In patients with essential hypertension compared to age-matched
healthy subjects, the endogenous concentration of circulating ELABELA was
found to be remarkably lower in hypertensive patients and negatively
correlated with systolic blood pressure and diastolic blood pressure. The fall in
endogenous ELA levels may be involved in the pathogenesis of hypertension-
related vascular damage.
hESCs
ELABELA is abundantly secreted by hESCs which do not
express APLNR. It reaches nM concentration in the extracellular
space and signals in an autocrine / paracrine manner.
By genetic deletion using CRISPR/Cas9, shRNA-mediated
inhibition or extracellular blockage
using neutralizing antibodies, endogenous ELA is shown to be
required for self-renewal of hESCs.
ELA binds to an unknown alternate receptor present at the cell
surface of hESCs and elicits immediate activation of the
PI3K/AKT pathway to promote hESCs survival.
Unlike Insulin, a growth factor added to hESCs culture medium,
ELA can poise hESCs towards the mesendoderm lineage.
Adult Physiology
ELABELA is expressed in adult kidney in mouse, rat and humans.
The ELA hormone circulates in blood where its half-life does not exceed
a few minutes. Injection of synthetic ELA in the bloodstream of rats
is sufficient to lower blood pressure and increase heart contractility.
ELA has hypotensive properties during pregnancy where it can lower
blood pressure, correct proteinuria and increase birth weight of mice
and pups lacking ELA.
The spliced mRNA of Elabela in mouse ES cells can bind
the hnRNPL protein. This does not need the ORF encoding for
the Ela peptide but instead its 3' UTR which functions a
regulatory RNA.
This non-coding function of murine Ela may not be conserved
in human ELA which has a very distinct 3' UTR length and
structure with the insertion of two Alu repeats.
Unique Identifiers:
AK092578
LOC100506013
Hs. 105196
OTTHUMT00000364313
OMIM:615594
ENSG00000248329
NM_001297550
cDNA FLJ35259 fis
clone PROST2004251
>human ELABELA cDNA (underlined is its ORF)
GCTTTTGGAGTACACTTCCACTAAAGTTATAGCATGCTTGAATGGTTTAT
TTCACCAATATTTGCTTATGGAAATAAAGGGGAGTGGCCGAGGAGAAAGG
AGAAGAGGAGTGGAGGAGGGGTTTGAGGCTGAGGGAGGCTCTGACCACAG
CACAGAGCACCGGCAACTTTGTCTAATGTGATCATTAACCTTCCTGCAAA
ACACAGCTGGCAGTTCTCTGAGGTTTGTCACTAGAATGTGAAGACAGCCA
CACAGATATTGCACAGACTATTTACAGATCGTTTGGTTTACATTGAGAGT
CATTGCTCTACTTTTGTGCGGTAGGAAAATGAGATTTCAGCAATTCCTTT
TTGCATTTTTTATTTTTATTATGAGTCTTCTCCTTATCAGCGGACAGAGA
CCAGTTAATTTGACCATGAGAAGAAAACTGCGCAAACACAATTGCCTTCA
GAGGAGATGTATGCCTCTCCATTCACGAGTACCCTTTCCCTGAGATCTCT
CTAGCTAACTTTACTGGATCTATCAGAAGAAGAAGAGGAGTGAAGGAAAG
ACACCCAGCCACACAAAAGAACTTCATGATGCCAACAGCGTGATTGCTTA
GAAGTTCCTACACAAAAAAAGGATCATTTGAAAGCACCTGGAATGGTTTA
TTAGCTTCACAGGATTTTATTCTTCTTGGCTTCTATTTGGAGGGAAAATA
ACATAAATTCAAAAGGATTCCAATCTGAAGCCCAAATCGTTTGCCTACAT
AACAAAAATATCTCATCTTTTCCTGCACATTATTATTCTTTTATGGGTTA
AAAAGAAAAATACCTTTTAGTGTTTTAGAACTCTCTCATGGTAAAAAGTG
CAAGAATTTAAAATGTTGCTTTCATATTCCTATAATTCTCCAAAAGTATT
AAATTCGTATATGTTTGAGTGATTTTCTAAAAACTGCTCAACCTGAAATC
AATTGCATTGACCATTTGGCTTCGCACAATAGGGAGAAAATAATTGGTTC
ATTGATTATATAGAGAGAAAGACTAAGAAAAGCTATTAATTGCTACCAAT
TTTATGATAAGCTTTAAGGTTTATGAAAGTATGTTTTTTTATTTAATGAG
TAATGTCCATTTGAAGTTGAAAGAAAACATGAAATCCTAATTGTAGTTCA
TTTTATGTTCAAATGAAACCATTGTTTTTGTTTTTGTTTTGAAACAGAGT
CTCACTCTGTTGCCCAAGGTGGAGAGAAGTGGCACGCTTTTGTCTCACTG
CAACCTCCACCTCCCGAGTTCAAGTGATTCTCGTGCCTCAACCTCCCAAT
TATAGGCTGGGATTACAGGTGTGCACCACTACACCCAGCTAATTCTTGTA
TTTTTTGTAGAGATGAGGTTTTACCCTGTTGCCCAGGCTGGTCTTGAACT
CAGGCTGGAACCATTCATTTTTTAACCTTTCTCATCATGTAATTATAGGA
ACCCAACGTTTGATTTCCTTTGAAGTTTTGTTATGTCCTTTATTATTTTG
TATGGATAATTTCTTTAAAAGTCTTACTTAAAGTTGACATCTAAAATACA
GTTATGCCAATGAAGTCCCACTCAGGGTGATATCTGTATCTAAAAGATGA
GTGCTCATCATCCTATTAGGCTTTGTCTTGGTGGTGTTCATCCTGAGATG
CTGAGACATGGAAATAAAAAATCAGAAGGAATTTAGGGATATGATTACTC
AAAAAAGAAACTATCCTGTCTAAATTTGAATTGTGTTGATAACTAGGTGT
TCCCCAGATGCTAAGATGTTCTTAATTTGTATTTATTGAAGGATTGTTAG
CTTAGTGCCACAAAATTTTTCTTACTTTATGTTAATTCCAGATAAGAAAT
TTACAAGTTTATATCTTTTTTTTTCTTTTTTTTAAGATGAGATCTGGCTC
TATCACCCAGGCTAAAGTGCAGTGGCATGATCTAGGCTAACTCCCTGGCT
CAAGCGATCCTTCCACCTCAGCCTCCCAAGTACCTGGGACTACAGGCACT
CACGGCCACACCTGACTAATTTTTGTATTTTTTTGTAGAGATGGAGTATC
GCCATGTTGCCCAGGTTGGTCTCAAACTCAGGCTGGTGAGCTCAAGTGAT
CCGCCTCCTTGGCCTCCCAAAATACTGGGATTACAGGCATGTGCCACCAT
GCTGGGCCACAAGTTCATATCTGGAGTAGAAGTTTTACTTTGTAAATATT
ATAAAGTAGAAGAAACCATAAACCATTTTGCTAAAATGAAAGGTTGGGGT
TAATATAAATGTAATTTTAAATAGAAAATCTGACAACACTGTCGAGTTTG
TCTTCCTGTCAAAGCTTATTAAAAGTGTCTTTGCGGATGAATGGTACTTT
CCACAAGTGCATTTGAGTAGAAGCATAACCTATTCTCAGTTATATTTATG
TTTAAAACATGTACTGGTTTGTATATTTTGTACTGAAAAAGAAAACACTT
TATAGTCAAGATACATCTCATTCAATACAAGTCTAAACTCTTTCAAATAC
AAATTCGCATATTCACAGAAAAAGTTACAAATCAGTTTTACTATTGTAAA
GTAATGAAATGGTTATACATTTCTTAATTGTTCAATAAAACACTCAATGA
TT