During embryogenesis, serotonin has been reported to be involved in craniofacial and cardiovascular morphogenesis. The detailed molecular mechanisms underlying these functions, however remain unknown. From mouse and human species, we have recently reported the cloning of 5-HT2B receptors which share signal transduction pathways with other 5-HT2 receptor subtypes (5-HT2A and 5-HT2C). In addition to phospholipase C stimulation, it appears that these three subtypes of receptor transduce a common serotonin-induced mitogenic activity, which could be important for cell differentiation and proliferation. We have first investigated the expression of 5-HT2 receptor mRNAs in the mouse embryo. Interestingly, a peak of 5-HT2B receptor mRNA expression was detected 8–9 days postcoitum, whereas there was only low level 5-HT2A and no 5-HT2C receptor mRNA expression at this stage. Expression of this receptor was confirmed by binding assays using a 5-HT2-specific ligand which revealed a peak of binding to membrane preparations from 9 days postcoitum embryos. In addition, whole mount in situ hybridisation and immunohistochemistry on similar stage embryos detected 5-HT2B expression in neural crest cells, heart myocardium and somites. The requirement for functional 5-HT2B receptors between 8 and 9 days postcoitum is supported by culture of embryos exposed to 5-HT2-specific ligands; 5-HT2B high-affinity antagonist such as ritanserin, induced morphological defects in the cephalic region, heart and neural tube. These antagonistic treatments interfere with cranial neural crest cell migration, induce their apoptosis, and are responsible for abnormal sarcomeric organisation of the subepicardial layer and for the absence of the trabecular cell layer in the ventricular myocardium. This report indicates for the first time that 5-HT2B receptors are actively mediating the action of serotonin on embryonic morphogenesis, probably by preventing the differentiation of cranial neural crest cells and myocardial precursor cells.

REFERENCES

REFERENCES
Bavik
C.
,
Ward
S.
,
Chambon
P.
(
1996
)
Developmental abnormalities in cultured mouse embryos deprived of retinoic acid by inhibition of yolk-sac retinol binding protein synthesis.
Proc. Natl. Acad. Sci. USA
93
,
3110
3114
Boess
F. G.
,
Martin
I. L.
(
1994
)
Molecular biology of 5-HT receptors.
Neuropharmacol
33
,
275
317
Brannan
C. I.
,
Perkins
A. S.
,
Vogel
K. S.
,
Ratner
N.
,
Nordlund
M. L.
,
Reid
S. W.
,
Buchberg
A. M.
,
Jenkins
N. A.
,
Parada
L. F.
,
Copeland
N. G.
(
1994
)
Targeted disruption of the neurofibromatosis type-1 gene leads to developmental abnormalities in heart and various neural crest-derived tissues.
Genes Dev
8
,
1019
1029
Bronner-Fraser
M.
(
1993
)
Mechanisms of neural crest cell migration.
BioEssays
15
,
221
230
Buc-Caron
M.-H.
,
Launay
J.-M.
,
Lamblin
D.
,
Kellermann
O.
(
1990
)
Serotonin uptake, storage, synthesis in an immortalised committed cell line derived from mouse teratocarcinoma.
Proc. Natl. Acad. Sci. USA
87
,
1922
1926
Choi
D.-S.
,
Birraux
G.
,
Launay
J.-M.
,
Maroteaux
L.
(
1994
)
The human serotonin 5-HT2B receptor: pharmacological link between 5-HT2 and 5-HT1D receptors.
FEBS Lett
352
,
393
399
Choi
D.-S.
,
Maroteaux
L.
(
1996
)
Immunohistochemical localisation of the serotonin 5-HT2B receptor in mouse gut, cardiovascular system, and brain.
FEBS Lett
391
,
45
51
Colas
J.-F.
,
Launay
J.-M.
,
Kellermann
O.
,
Rosay
P.
,
Maroteaux
L.
(
1995
)
Drosophila serotonin 5-HT2 receptor: Coexpression with fushi-tarazu during segmentation.
Proc. Natl. Acad. Sci. USA
92
,
5441
5445
Goulding
M. D.
,
Lumsden
A.
,
Gruss
P.
(
1993
)
Signals from the notochord and floor plate regulate the region-specific expression of two pax genes in the developing spinal cord.
Development
117
,
1001
1016
Graham
A.
,
Francis-West
P.
,
Brickell
P.
,
Lumsden
A.
(
1994
)
The signalling molecule BMP4 mediates apoptosis in the rhombencephalic neural crest.
Nature
372
,
684
686
Graham
A.
,
Heyman
I.
,
Lumsden
A.
(
1993
)
Even-numbered rhombomeres control the apoptotic elimination of neural crest cells from odd-numbered rhombomeres in chick hindbrain.
Development
119
,
233
245
Hellendall
R. P.
,
Schambra
U. B.
,
Liu
J. P.
,
Lauder
J. M.
(
1993
)
Prenatal expression of 5-HT1C and 5-HT2 receptors in the rat central nervous system.
Exp. Neurol
120
,
186
201
Henkemeyer
M.
,
Rossi
D. J.
,
Holmyard
D. P.
,
Puri
M. C.
,
Mbamalu
G.
,
Harpal
K.
,
Shih
T. S.
,
Jacks
T.
,
Pawson
T.
(
1995
)
Vascular system defects and neuronal apoptosis in mice lacking Ras-GTPase-activating protein.
Nature
377
,
695
701
Hoyer
D.
,
Fozard
J. R.
,
Saxena
P. R.
,
Mylecharane
E. J.
,
Clarke
D. E.
,
Martin
G. R.
,
Humphrey
P. P. A.
(
1994
)
IUPHAR classification of receptors for 5-hydroxytryptamine (serotonin).
Pharmacol. Rev
46
,
157
203
Huether
G.
,
Rittner
I.
,
Reimer
A.
,
Adler
L.
,
Youdim
M. B. H.
(
1992
)
Early appearance of serotonin in the embryonal circulation and its action on the developing cardiovascular system of the chick embryo.
Biog. Amines
8
,
421
430
Jeffs
P.
,
Jaques
K.
,
Osmond
M.
(
1992
)
Cell death in cranial neural crest development.
Anat. Embryol
185
,
583
588
Julius
D.
,
Livelli
T. J.
,
Jessell
T. M.
,
Axel
R.
(
1989
)
Ectopic expression of the serotonin 1C receptor and the triggering of malignant transformation.
Science
244
,
1057
1062
Kastner
P.
,
Grondona
J.
,
Mark
M.
,
Gansmuller
A.
,
Le Meur
M.
,
Decimo
D.
,
Vonesch
J.
,
Dolle
P.
,
Chambon
P.
(
1994
)
Genetic analysis of RXR alpha developmental function: convergence of RXR and RAR signalling pathways in heart and eye morphogenesis.
Cell
78
,
987
1003
Kellermann
O.
,
Loric
S.
,
Maroteaux
L.
,
Launay
J.-M.
(
1996
)
Sequential onset of three 5-HT receptors during the 5-hydroxytryptaminergic differentiation of the murine 1C11 cell line.
Br. J. Pharmacol
118
,
1161
1170
Lauder
J. M.
(
1988
)
Neurotransmitters as morphogens.
Prog. Brain Res
73
,
365
387
Lauder
J. M.
(
1993
)
Neurotransmitters as growth regulatory signals: role of receptors and second messengers.
Tr. Neurosci
16
,
233
240
Lauder
J. M.
,
Tamir
H.
,
Sadler
T. W.
(
1988
)
Serotonin and morphogenesis: I. Sites of serotonin uptake and-binding protein immunoreactivity in the midgestation mouse embryo.
Development
102
,
709
720
Lauder
J. M.
,
Zimmerman
E. F.
(
1988
)
Sites of serotonin uptake in epithelia of the developing mouse palate, oral cavity, and face: possible role in morphogenesis.
J. Craniofac. Genet. Dev. Biol
8
,
265
276
Launay
J.-M.
,
Birraux
G.
,
Bondoux
D.
,
Callebert
J.
,
Choi
D.-S.
,
Loric
S.
,
Maroteaux
L.
(
1996
)
Ras involvement in signal transduction by the serotonin 5-HT2B receptor.
J. Biol. Chem
271
,
3141
3147
Le Douarin
N. M.
,
Ziller
C.
,
Couly
G. F.
(
1993
)
Patterning of neural crest derivatives in the avian embryo: in vivo and in vitro studies.
Dev. Biol
159
,
24
49
LeConiat
M.
,
Choi
D.-S.
,
Maroteaux
L.
,
Launay
J.-M.
,
Berger
R.
(
1996
).
The 5-HT2B receptor gene maps to 2q36.3-2q37.1.
Genomics
32
,
173
175
Lemke
G.
(
1996
)
Neuregulins in development.
Mol. Cell. Neurosci
7
,
247
262
Lenke
R. R.
,
Levy
H. R.
(
1980
)
Maternal phenylketonuria and hyperphenylalaninemia: an international survey of the outcome of untreated and treated pregnancies.
New Eng. J. Med
303
,
1202
1208
Loric
S.
,
Launay
J.-M.
,
Colas
J.-F.
,
Maroteaux
L.
(
1992
)
New mouse 5-HT2-like receptor: Expression in brain, heart, and intestine.
FEBS Lett
312
,
203
207
Loric
S.
,
Maroteaux
L.
,
Kellermann
O.
,
Launay
J.-M.
(
1995
)
Functional serotonin-2B receptors are expressed by a teratocarcinoma-derived cell line during serotoninergic differentiation.
Mol. Pharmacol
47
,
458
466
Lumsden
A.
,
Sprawson
N.
,
Graham
A.
(
1991
)
Segmental origin and migration of neural crest cells in the hindbrain region of the chick embryo.
Development
113
,
1281
1291
Mark
M.
,
Lufkin
T.
,
Vonesch
J.-L.
,
Ruberte
E.
,
Olivo
J.-C.
,
Dolle
P.
,
Gorry
P.
,
Lumsden
A.
,
Chambon
P.
(
1993
)
Two rhombomeres are altered in Hoxa-1 null mutant mice.
Development
119
,
319
338
Moiseiwitsch
J. R. D.
,
Lauder
J. M.
(
1995
)
Serotonin regulates mouse cranial neural crest migration.
Proc. Natl. Acad. Sci. USA
92
,
7182
7186
Morriss-Kay
G. M.
,
Tan
S.-S.
(
1987
)
Mapping cranial neural crest cell migration in mammalian embryos.
Tr. Genet
3
,
257
261
New
D. A. T.
(
1990
)
Whole embryo culture, teratogenesis and the estimation of teratologic risk.
Teratology
42
,
635
642
Newgreen
D. F.
,
Minichiello
J.
(
1995
)
Control of epitheliomesenchymal transformation. I. Events in the onset of neural crest cell migration are separable and inducible by protein kinase inhibitors.
Dev. Biol
170
,
91
101
Perry
W. L.
III
,
Vasicek
T. J.
,
Lee
J. J.
,
Rossi
J. M.
,
Zeng
L.
,
Zhang
T.
,
Tilghman
S. M.
,
Costantini
F.
(
1995
)
Phenotypic and molecular analysis of a transgenic insertional allele of the mouse fused locus.
Genetics
141
,
321
332
Pourquie
O.
,
Coltey
M.
,
Breant
C.
,
Le Douarin
N. M.
(
1995
)
Control of somite patterning by signals from the lateral plate.
Proc. Natl. Acad. Sci. USA
92
,
3219
3223
Selleck
M. A. J.
,
Bronner-Fraser
M.
(
1996
)
The genesis of avian neural crest cells: A classic embryonic induction.
Proc. Natl. Acad. Sci. USA
93
,
9352
9357
Shorle
H.
,
Meier
P.
,
Buchert
M.
,
Jaenisch
R.
,
Mitchell
P. J.
(
1996
)
Transcription factor AP-2 essential for cranial closure and craniofacial development.
Nature
381
,
235
238
Shuey
D. L.
,
Sadler
T. W.
,
Tamir
H.
,
Lauder
J. M.
(
1993
)
Serotonin andmorphogenesis-Transient expression of serotonin uptake and binding protein during craniofacial morphogenesis in the mouse.
Anat. Embryol
187
,
75
85
Tecott
L. H.
,
Sun
L. M.
,
Akana
S. F.
,
Strack
A. M.
,
Lowenstein
D. H.
,
Dallman
M. F.
,
Julius
D.
(
1995
)
Eating disorder and epilepsy in mice lacking 5-HT2C serotonin receptors.
Nature
374
,
542
546
Van Cauteren
H.
,
Van Denberghe
J.
,
Marsboom
R.
(
1986
)
Protective activity of ketanserin against serotonin-induced embryotoxicity and teratogenicity in rats.
Drug Dev. Res
8
,
179
185
Wehr
R.
,
Gruss
P.
(
1996
)
Pax and vertebrate development.
Int. J. Dev. Biol
40
,
369
377
Yavarone
M. S.
,
Shuey
D. L.
,
Sadler
T. W.
,
Lauder
J. M.
(
1993
)
Serotonin uptake in the ectoplacental cone and placenta of the mouse.
Placenta
14
,
149
161
Yavarone
M. S.
,
Shuey
D. L.
,
Tamir
H.
,
Sadler
T. W.
,
Lauder
J.M.
(
1993
)
Serotonin and cardiac morphogenesis in the mouse embryo.
Teratology
47
,
573
584
Zhang
J.
,
Hagopian-Donaldson
S.
,
Serbedzija
G.
,
Elsemore
J.
,
Plehn-Dujowich
D.
,
McMahon
A. P.
,
Flavell
R. A.
,
Williams
T.
(
1996
)
Neural tube, skeletal and body wall defects in mice lacking transcription factor AP-2.
Nature
381
,
238
241
This content is only available via PDF.