Éditeur(s) : HAL CCSD Springer International Publishing
Résumé : International audience
This two-volume book set focuses on the Siberian sturgeon. Acipenser baerii Brandt 1869, one of the 27 “existing” sturgeon species, is a native species of the Siberian catchments, where – as in many other parts of the world – the sturgeon populations are now threatened. Sturgeon farming practices targeting caviar and meat production have been expanding worldwide since the 1990s, and have seen a further increase since the turn of the century. Among the handful of sturgeon species used for significant production, the most dominant is the Siberian sturgeon. Given its peculiar phylogenetic position as a chondrostei and its use as a biological model in e.g. France, the species has also attracted the attention of biologists.
The Siberian Sturgeon (Acipenser baerii, Brandt, 1869)

ISBN : 978-3-319-61925-5
hal-01563969
http://hal.upmc.fr/hal-01563969

Éditeur(s) : HAL CCSD SAGE Publications (UK and US)
Résumé : International audience
Amelogenin gene organization varies from 6 exons (1,2,3,5,6,7) in amphibians and sauropsids to 10 in rodents. The additional exons are exons 4, 8, 9, and ``4b'', the latter being as yet unidentified in AMELX transcripts. To learn more about the evolutionary origin of these exons, we used an in silico approach to find them in 39 tetrapod genomes. AMEL organization with 6 exons was the ancestral condition. Exon 4 was created in an ancestral therian (marsupials + placentals), then exon 9 in an ancestral placental, and finally exons ``4b'' and 8 in rodents, after divergence of the squirrel lineage. These exons were either inactivated in some lineages or remained functional: Exon 4 is functional from artiodactyls onward; exon 9 is known, to date, only in rodents, but could be coding in various mammals; and exon ``4b'' was probably coding in some rodents. We performed PCR of cDNA isolated from mouse and human tooth buds to identify the presence of these transcripts. A sequence analogous to exon ``4b'', and to exon 9, could not be amplified from the respective tooth cDNA, indicating that even though sequences similar to these exons are present, they are not transcribed in these species.
ISSN: 0022-0345

hal-01545487
https://hal.archives-ouvertes.fr/hal-01545487
DOI : 10.1177/0022034511423399

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
The evolutionary origin of teeth from dermal denticles (odontodes) that developed in the mouth cavity, designated as outside-in hypothesis, has long been undisputed. The outside-in hypothesis is based on the conclusion that dermal denticles and teeth fulfil the criteria of homology in an exemplary manner. Over the past 15 years, this hypothesis has been challenged. Proponents of the alternative inside-out hypothesis suggest that teeth did not evolve from dermal denticles, that they are of endodermal origin (forming in conjunction with neural crest-derived mesenchyme) and that they evolved several times independently in different lineages of vertebrates. Key arguments for the inside-out hypothesis are mineralized structures of conodonts that are accepted as teeth, the exclusive acceptance of placoderm pharyngeal denticles as teeth, together with the rejection of the presence of teeth in basal placoderms. We summarize the results of recent studies that have been triggered by the fruitful discussion between the two conflicting hypotheses. New findings support the traditional outside-in hypothesis: the mineralized elements of conodonts are not teeth, and the oral cusps in basal placoderms are true teeth. Furthermore, new developmental and molecular data clarify homology between teeth and dermal denticles. Today a new synthesis is emerging about the evolutionary origin of teeth from dermal denticles and about the unity of the elements of the dermal skeleton.
ISSN: 0175-8659

hal-01545480
https://hal.archives-ouvertes.fr/hal-01545480
DOI : 10.1111/jai.12532

Éditeur(s) : HAL CCSD SAGE Publications (UK and US)
Résumé : International audience
Molecular evolutionary analysis is an efficient method to predict and/or validate amino acid substitutions that could lead to a genetic disease and to highlight residues and motifs that could play an important role in the protein structure and/or function. We have applied such analysis to amelotin (AMTN), a recently identified enamel protein in the rat, mouse, and humans. An in silico search for AMTN provided 42 new mammalian sequences that were added to the 3 published sequences with which we performed the analysis using a dataset representative of all lineages (circa 220 million years of evolution), including 2 enamel-less species, sloth and armadillo. During evolution, of the 209 residues of human AMTN, 17 were unchanged and 34 had conserved their chemical properties. Substituting these important residues could lead to amelogenesis imperfecta (AI). Also, AMTN possesses a well-conserved signal peptide, 2 conserved motifs whose function is certainly important but unknown, and a putative phosphorylation site (SXE). In addition, the sequences of the 2 enamel-less species display mutations revealing that AMTN underwent pseudogenization, which suggests that AMTN is an enamel-specific protein.
ISSN: 0022-0345

hal-01545488
https://hal.archives-ouvertes.fr/hal-01545488
DOI : 10.1177/0022034512460551

Éditeur(s) : HAL CCSD SAGE Publications (UK and US)
Résumé : International audience
In this article, we focus on hypomaturation autosomal-recessive-type amelogenesis imperfecta (type IIA2) and describe 2 new causal Matrix metalloproteinase 20 (MMP20) mutations validated in two unrelated families: a missense mutation p.T130I at the expected homozygous state, and a compound heterozygous mutation having the same mutation combined with a nucleotide deletion, leading to a premature stop codon (p.N120fz*2). We characterized the enamel structure of the latter case using scanning electron microscopy analysis and microanalysis (Energy-dispersive X-ray Spectroscopy, EDX) and confirmed the hypomaturation-type amelogenesis imperfecta as identified in the clinical diagnosis. The mineralized content was slightly decreased, with magnesium substituting for calcium in the crystal structure. The anomalies affected enamel with minimal inter-rod enamel present and apatite crystals perpendicular to the enamel prisms, suggesting a possible new role for MMP20 in enamel formation.
ISSN: 0022-0345

hal-01545484
https://hal.archives-ouvertes.fr/hal-01545484
DOI : 10.1177/0022034513488393

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Tuftelin (TUFT1) is an acidic, phosphorylated glycoprotein, initially discovered in developing enamel matrix. TUFT1 is expressed in many mineralized and non-mineralized tissues. We performed an evolutionary analysis of 82 mammalian TUFT1 sequences to identify residues and motifs that were conserved during 220 million years (Ma) of evolution. We showed that 168 residues (out of the 390 residues composing the human TUFT1 sequence) are under purifying selection. Our analyses identified several, new, putatively functional domains and confirmed previously described functional domains, such as the TIP39 interaction domain, which correlates with nuclear localization of the TUFT1 protein, that was demonstrated in several tissues. We also identified several sites under positive selection, which could indicate evolutionary changes possibly related to the functional diversification of TUFT1 during evolution in some lineages. We discovered that TUFT1 and MYZAP (myocardial zonula adherens protein) share a common ancestor that was duplicated circa 500 million years ago. Taken together, these findings expand our knowledge of TUFT1 evolution and provide new information that will be useful for further investigation of TUFT1 functions.
ISSN: 0022-2844

hal-01516886
http://hal.upmc.fr/hal-01516886
http://hal.upmc.fr/hal-01516886/document
http://hal.upmc.fr/hal-01516886/file/Delgado_2017_Evolutionary.pdf
DOI : 10.1007/s00239-017-9789-5

Éditeur(s) : HAL CCSD SAGE Publications (UK and US)
Résumé : International audience
Enamel and enameloid, the highly mineralized tooth-covering tissues in living vertebrates, are different in their matrix composition. Enamel, a unique product of ameloblasts, principally contains enamel matrix proteins (EMPs), while enameloid possesses collagen fibrils and probably receives contributions from both odontoblasts and ameloblasts. Here we focused on type I collagen (COL1A1) and amelogenin (AMEL) gene expression during enameloid and enamel formation throughout ontogeny in the caudate amphibian, Pleurodeles waltl. In this model, pre-metamorphic teeth possess enameloid and enamel, while post-metamorphic teeth possess enamel only. In first-generation teeth, qPCR and in situ hybridization (ISH) on sections revealed that ameloblasts weakly expressed AMEL during late-stage enameloid formation, while expression strongly increased during enamel deposition. Using ISH, we identified COL1A1 transcripts in ameloblasts and odontoblasts during enameloid formation. COL1A1 expression in ameloblasts gradually decreased and was no longer detected after metamorphosis. The transition from enameloid-rich to enamel-rich teeth could be related to a switch in ameloblast activity from COL1A1 to AMEL synthesis. P. waltl therefore appears to be an appropriate animal model for the study of the processes involved during enameloid-to-enamel transition, especially because similar events probably occurred in various lineages during vertebrate evolution.
ISSN: 0022-0345

hal-01545475
https://hal.archives-ouvertes.fr/hal-01545475
DOI : 10.1177/0022034514526236

Éditeur(s) : HAL CCSD SAGE Publications (UK and US)
Résumé : International audience
In the literature, the enamelin gene ENAM has been repeatedly designated as a possible candidate for caries susceptibility. Here, we checked whether ENAM variants could increase caries susceptibility. To this aim, we sequenced coding exons and exon-intron boundaries of ENAM in 250 children with a severe caries phenotype and in 149 caries-free patients from 9 French hospital groups. In total, 23 single-nucleotide polymorphisms (SNPs) were found, but none appeared to be responsible for a direct change of ENAM function. Six SNPs had a high minor allele frequency (MAF) and 6 others were identified for the first time. Statistical and evolutionary analyses showed that none of these SNPs was associated with caries susceptibility or caries protection when studied separately and challenged with environmental factors. However, haplotype interaction analysis showed that the presence, in a same variant, of 2 exonic SNPs (rs7671281 and rs3796704; MAF 0.12 and 0.10, respectively), both changing an amino acid in the protein region encoded by exon 10 (p.I648T and p.R763Q, respectively), increased caries susceptibility 2.66-fold independent of the environmental risk factors. These findings support ENAM as a gene candidate for caries susceptibility in the studied population.
ISSN: 0022-0345

hal-01545476
https://hal.archives-ouvertes.fr/hal-01545476
DOI : 10.1177/0022034514522060

Éditeur(s) : HAL CCSD SAGE Publications (UK and US)
Résumé : International audience
Genetic approaches have shown that several genes could modify caries susceptibility; AmelogeninX (AMELX) has been repeatedly designated. Here, we hypothesized that AMELX mutations resulting in discrete changes of enamel microstructure may be found in children with a severe caries phenotype. In parallel, possible AMELX mutations that could explain resistance to caries may be found in caries-free patients. In this study, coding exons of AMELX and exon-intron boundaries were sequenced in 399 individuals with extensive caries (250) or caries-free (149) individuals from nine French hospital groups. No mutation responsible for a direct change of amelogenin function was identified. Seven single-nucleotide polymorphisms (SNPs) were found, 3 presenting a high allele frequency, and 1 being detected for the first time. Three SNPs were located in coding regions, 2 of them being non-synonymous. Both evolutionary and statistical analyses showed that none of these SNPs was associated with caries susceptibility, suggesting that AMELX is not a gene candidate in our studied population.
ISSN: 0022-0345

hal-01545481
https://hal.archives-ouvertes.fr/hal-01545481
DOI : 10.1177/0022034513482941

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
We review current knowledge of axial skeleton biology in Acipenseriformes with the aim to know whether available data can help in understanding axial anomalies (anomalies of the vertebral column) in reared sturgeons or if further investigations are needed prior to undertake such analysis. In particular, accurate data on axial skeleton development, structure and mineralization are required to understand these pathologies. We show that such knowledge is fragmented and incomplete when compared to the information available in teleost fish. In Acipenseriformes, we only know that (i) the axial skeleton morphology is highly distinctive, as mostly cartilaginous, (ii) the vertebrae are composed of several elements organized around a persistent and unconstricted notochord, and (iii) mineralization only concerns a few of these elements and occurs late in ontogeny, but virtually no descriptions demonstrating the presence of bone (perichondral, membranous...) or mineralized cartilage is available in the literature. In addition, few studies concern axial anomalies in the wild or in rearing conditions, and the determinism of these pathologies is largely unknown. This is in contrast with the numerous studies dealing with the axial skeleton and its anomalies in many farmed teleost species, in which axial anomalies can result from numerous factors, such as unfavourable abiotic conditions, inappropriate nutrition and genetic factors. However, even if some parallels can be established between teleosts and sturgeons, it appears that current knowledge of the axial skeleton in teleosts may not help much in the study of axial anomalies in sturgeons. Knowledge of axial skeleton biology in sturgeon has to be therefore deeply improved prior to undertake investigations focusing on these pathologies.
ISSN: 0175-8659

hal-01545478
https://hal.archives-ouvertes.fr/hal-01545478
DOI : 10.1111/jai.12525