The role of serotonin and neurotransmitters during craniofacial development

Cannabidiol disrupts tryptophan metabolism in the human term placenta

The increasing use of cannabis during pregnancy raises concerns about its impact on fetal development. While cannabidiol (CBD) shows therapeutic promise, its effects during pregnancy remain uncertain. We investigated CBD's influence on tryptophan (TRP) metabolism in the human placenta. TRP is an essential amino acid that is metabolized via the serotonin and kynurenine (KYN) pathways, which are critical for fetal neurodevelopment. We used human term villous placental explants, an advanced ex vivo model, to study CBD's impact on key TRP metabolic enzymes. In addition, vesicles isolated from the microvillous membrane (MVM) of the human placenta were used to assess CBD's effect on placental serotonin uptake. Explants were exposed to CBD at therapeutic (0.1, 1, 2.5 μg/ml) and non-therapeutic (20 and 40 μg/ml) concentrations to determine its effects on the gene and protein expression of key enzymes in TRP metabolism and metabolite release. CBD upregulated TRP hydroxylase (TPH) and downregulated monoamine oxidase (MAO-A), resulting in reduced levels of 5-hydroxyindoleacetic acid (HIAA). It also downregulated serotonin transporter expression and inhibited serotonin transport across the MVM by up to 60% while simultaneously enhancing TRP metabolism via the kynurenine pathway by upregulating indoleamine-pyrrole 2,3-dioxygenase (IDO-1). Among kynurenine pathway enzymes, kynurenine 3 monooxygenase (KMO) was upregulated while kynurenine aminotransferase 1 (KAT-1) was downregulated; the former is associated with neurotoxic metabolite production, while the latter is linked to reduced neuroprotective metabolite levels. Overall, these results indicate that CBD modulates TRP catabolism in the human placenta, potentially disrupting the tightly regulated homeostasis of the serotonin and KYN pathways.

CHD7 regulates craniofacial cartilage development via controlling HTR2B expression

Mutations in the Chromodomain helicase DNA-binding protein 7 - coding gene (CHD7) cause CHARGE syndrome (CS). Although craniofacial and skeletal abnormalities are major features of CS patients, the role of CHD7 in bone and cartilage development remain largely unexplored. Here, using a zebrafish (Danio rerio) CS model, we show that chd7-/- larvae display abnormal craniofacial cartilage development and spinal deformities. The craniofacial and spine defects are accompanied by a marked reduction of bone mineralization. At the molecular level, we show that these phenotypes are associated with significant reduction in the expression levels of osteoblast differentiation markers. Additionally, we detected a marked depletion of collagen 2α1 in the cartilage of craniofacial regions and vertebrae, along with significantly reduced number of chondrocytes. Chondrogenesis defects are at least in part due to downregulation of htr2b, which we found to be also dysregulated in human cells derived from an individual with CHD7 mutation-positive CS. Overall, this study thus unveils an essential role for CHD7 in cartilage and bone development, with potential clinical relevance for the craniofacial defects associated with CS.

Physiopathologic Bases of Moebius Syndrome: Combining Genetic, Vascular, and Teratogenic Theories

Moebius syndrome (MBS) is a congenital cranial dysinnervation disorder (CCDD) characterized by a bilateral palsy of abducens and facial cranial nerves, which may coexist with other cranial nerves palsies, mostly those found in the dorsal pons and medulla oblongata. MBS is considered a "rare" disease, occurring in only 1:50,000 to 1:500,000 live births, with no gender predominance. Three independent theories have been described to define its etiology: the vascular theory, which talks about a transient blood flow disruption; the genetic theory, which takes place due to mutations related to the facial motor nucleus neurodevelopment; and last, the teratogenic theory, associated with the consumption of agents such as misoprostol during the first trimester of pregnancy. Since the literature has suggested the existence of these theories independently, this review proposes establishing a theory by matching the MBS molecular bases. This review aims to associate the three etiopathogenic theories at a molecular level, thus submitting a combined postulation. MBS is most likely an underdiagnosed disease due to its low prevalence and challenging diagnosis. Researching other elements that may play a key role in the pathogenesis is essential. It is common to assume the difficulty that patients with MBS have in leading an everyday social life. Research by means of PubMed and Google Scholar databases was carried out, same in which 94 articles were collected by using keywords with the likes of "Moebius syndrome," "PLXND1 mutations," "REV3L mutations," "vascular disruption AND teratogens," and "congenital facial nerve palsy." No exclusion criteria were applied.

Tryptophan Hydroxylase-2-Mediated Serotonin Biosynthesis Suppresses Cell Reprogramming into Pluripotent State

The monoamine neurotransmitter serotonin (5-hydroxytryptamine, 5-HT) has important functions both in the neural system and during embryonic development in mammals. In this study, we set out to investigate whether and how endogenous serotonin affects reprogramming to pluripotency. As serotonin is synthesized from tryptophan by the rate limiting enzymes tryptophan hydroxylase-1 and -2 (TPH1 and TPH2), we have assessed the reprogramming of TPH1- and/or TPH2-deficient mouse embryonic fibroblasts (MEFs) to induced pluripotent stem cells (iPSCs). The reprogramming of the double mutant MEFs showed a dramatic increase in the efficiency of iPSC generation. In contrast, ectopic expression of TPH2 alone or in conjunction with TPH1 reverted the rate of reprogramming of the double mutant MEFs to the wild-type level and besides, TPH2 overexpression significantly suppressed reprogramming of wild-type MEFs. Our data thus suggest a negative role of serotonin biosynthesis in the reprogramming of somatic cells to a pluripotent state.

Prenatal exposure to sertraline, associated or not with stress, can negatively program somatic and neurobehavioral development of female rats, and dysregulate reproductive function in adulthood

Selective serotonin reuptake inhibitors (SSRIs) are prescribed to pregnant women for treating mental illnesses. Among the drugs of this class, sertraline (ST) is the antidepressant therapy recommended most frequently. Therefore, this study aimed to evaluate the impact of gestational ST treatment on reproductive parameters and toxicological target organs of rat female offspring, as well as on somatic, reflex and neurobehavioral development, in a model of maternal adversity. Pregnant Wistar rats received vehicle (filtered water) or ST hydrochloride (20 mg/Kg/day diluted in vehicle) by oral gavage, associated or not with restraint stress for 1 h/day from gestational days 13-20. F1 female offspring was evaluated on reproductive parameters, body weight and somatic and reflex milestones from postnatal day (PND) 1. On PNDs 25 and 72, the elevated-plus-maze test was performed, while toxicological target organs were evaluated on PNDs 42 and 80. In utero exposure to ST, regardless of exposure to stress, reduced body weight at birth and affected the somatic development and estrous cycle. The absolute and relative thyroid weights were increased in Stress/ST group during puberty and adulthood, while the percentage of ovarian structures and the absolute uterine weight were altered in this group on PND 80. Prenatal exposure only to ST reduced initial body weight gain, delayed fur development and increased anxiety-like behavior on PND 25. Thus, this experimental study suggests that intrauterine exposure to ST disrupts the fetal environment and can negatively program serotonin-regulated processes. Furthermore, it impacts thyroid weight when associated with stress.

Development of the Placenta and Brain Are Affected by Selective Serotonin Reuptake Inhibitor Exposure During Critical Periods

Selective serotonin reuptake inhibitors (SSRIs) are usually prescribed to treat major depression and anxiety disorders. Fetal brain development exhibits dependency on serotonin (5-hydroxytryptamine, 5-HT) from maternal, placental, and fetal brain sources. At very early fetal stages, fetal serotonin is provided by maternal and placental sources. However, in later fetal stages, brain sources are indispensable for the appropriate development of neural circuitry and the rise of emergent functions implied in behavior acquisition. Thus, susceptible serotonin-related critical periods are recognized, involving the early maternal and placental 5-HT synthesis and the later endogenous 5-HT synthesis in the fetal brain. Acute and chronic exposure to SSRIs during these critical periods may result in short- and long-term placental and brain dysfunctions affecting intrauterine and postnatal life. Maternal and fetal cells express serotonin receptors which make them susceptible to changes in serotonin levels influenced by SSRIs. SSRIs block the serotonin transporter (SERT), which is required for 5-HT reuptake from the synaptic cleft into the presynaptic neuron. Chronic SSRI administration leads to pre- and postsynaptic 5-HT receptor rearrangement. In this review, we focus on the effects of SSRIs administered during critical periods upon placentation and brain development to be considered in evaluating the risk-safety balance in the clinical use of SSRIs.

The roles of serotonin in cell adhesion and migration, and cytoskeletal remodeling

Serotonin is well known as a neurotransmitter. Its roles in neuronal processes such as learning, memory or cognition are well established, and also in disorders such as depression, schizophrenia, bipolar disorder, and dementia. However, its effects on adhesion and cytoskeletal remodelling which are strongly affected by 5-HT receptors, are not as well studied with some exceptions for e.g. platelet aggregation. Neuronal function is strongly dependent on cell-cell contacts and adhesion-related processes. Therefore the role played by serotonin in psychiatric illness, as well as in the positive and negative effects of neuropsychiatric drugs through cell-related adhesion can be of great significance. In this review, we explore the role of serotonin in some of these aspects based on recent findings.

Serotonin contributes to the in vitro production of a biomimetic enamel-like material from reprogrammed oral epithelial keratinocytes

OBJECTIVES

To evaluate the role of serotonin in the development of a biomimetic enamel-like material in vitro.

SETTING AND SAMPLE POPULATION

Immortalized murine oral keratinocytes raised from adult mouse mucosa were cultured in vitro. In addition, specimens incorporating molar tooth buds harvested from mice were included in our studies.

MATERIALS AND METHODS

We used cell-based scaffold-free tissue engineering to assemble three-dimensional (3D) organoids into complex tissue constructs that closely emulate the complexity of adult enamel. We also analysed mouse molar specimens using immunohistochemistry for serotonin expression as well as its cognate receptor.

RESULTS

TGF-β1-reprogrammed murine oral keratinocytes formed organoids that laid down an amelogenin-rich protein matrix when grown as three-dimensional (3D) cultures in the presence of serotonin. Following mineralization, the newly formed crystals were densified under pressure and vacuum to produce a biomimetic enamel-like material that demonstrated parallel alignment of hydroxyapatite crystals with some interspaced residual organoid matter into enamel prism-like structures conferring size, mechanical properties comparable to tooth enamel, including light translucency. Serotonin expression was localized by immunohistochemistry proximal to the enamel organ of developing molar buds. Moreover, serotonin HTRb2 receptor expression was localized on ameloblasts within the enamel organ proximal to the area where serotonin was immunolocalized.

CONCLUSIONS

Our results demonstrate that serotonin is inductive in the development of a biomimetic enamel-like material from reprogrammed oral epithelial keratinocytes in vitro. The facileness of harvesting adult somatic cells together with the versatility of our approach offers exciting opportunities to address regenerative challenges linked to lost enamel.

A mutation in monoamine oxidase (MAO) affects the evolution of stress behavior in the blind cavefish Astyanax mexicanus

The neurotransmitter serotonin controls a variety of physiological and behavioral processes. In humans, mutations affecting monoamine oxidase (MAO), the serotonin-degrading enzyme, are highly deleterious. Yet, blind cavefish of the species Astyanax mexicanus carry a partial loss-of-function mutation in MAO (P106L) and thrive in their subterranean environment. Here, we established four fish lines, corresponding to the blind cave-dwelling and the sighted river-dwelling morphs of this species, with or without the mutation, in order to decipher the exact contribution of mao P106L in the evolution of cavefish neurobehavioral traits. Unexpectedly, although mao P106L appeared to be an excellent candidate for the genetic determinism of the loss of aggressive and schooling behaviors in cavefish, we demonstrated that it was not the case. Similarly, the anatomical variations in monoaminergic systems observed between cavefish and surface fish brains were independent from mao P106L, and rather due to other, morph-dependent developmental processes. However, we found that mao P106L strongly affected anxiety-like behaviors. Cortisol measurements showed lower basal levels and an increased amplitude of stress response after a change of environment in fish carrying the mutation. Finally, we studied the distribution of the P106L mao allele in wild populations of cave and river A. mexicanus, and discovered that the mutant allele was present - and sometimes fixed - in all populations inhabiting caves of the Sierra de El Abra. The possibility that this partial loss-of-function mao allele evolves under a selective or a neutral regime in the particular cave environment is discussed.

The teratogenic effects of sertraline in mice

BACKGROUND

Selective serotonin reuptake inhibitors (SSRIs), which include paroxetine (Paxil), sertraline (Zoloft), fluoxetine (Prozac), citalopram (Celexa), and escitalopram (Lexapro), are the most common antidepressants prescribed to pregnant women. There is considerable debate in the literature regarding the developmental toxicities of SSRIs individually, and as a class.

METHODS

It is considered unethical to perform developmental toxicity studies on pregnant women, but rodent and nonrodent species provide laboratory-controlled experimental models to examine the toxicity of SSRI exposure during pregnancy. The Embryo-Fetal Developmental Toxicity Study was conducted with sertraline in mice, Crl:CD1 (lCR), during the period of organogenesis.

RESULTS

Increased resorption rates, lower fetal weight, and increased percentage of fetuses with visceral and skeletal abnormalities were found in the intermediate and high sertraline dose groups. In addition to incomplete ossification of treated animals, eleven sertraline exposed fetuses, two in group 2 (5 mg/kg), five in group 3 (25 mg/kg), and four in group 4 (60 mg/kg), had cleft palate (CP). This malformation was not observed in any controls. Only the highest dose of sertraline was found to be maternally toxic, as evidenced by significantly lower weight gain during pregnancy.

CONCLUSION

These data indicate that in utero exposure to sertraline at 25 and 60 mg/kg was embryotoxic, teratogenic, and fetotoxic in mice. The incidence of CP observed in groups 3 and 4 (2.99% and 2.5%, respectively) were higher than the maximum range value noted in historical controls and indicate sertraline is a teratogen in ICR mice.

Treatment with the essential amino acid L-tryptophan reduces masticatory impairments in experimental cerebral palsy

Purpose Children with cerebral palsy (CP) often exhibit difficulties in feeding resulting from deficits in chewing. This study investigates the therapeutic potential of L-tryptophan (TRI) to reduce deficits in chewing in rats subjected to an experimental model of CP.Methods A total of 80 Wistar albino rats were used. Pups were randomly assigned to 4 experimental groups: Control Saline, Control TRI, CP Saline, and CP TRI groups. The experimental model of CP was based on the combination of perinatal anoxia associated with postnatal sensorimotor restriction of the hind limbs. TRI was administered subcutaneously during the lactation period. Anatomical and behavioral parameters were evaluated during maturation, including body weight gain, food intake, chewing movements, relative weight and the distribution of the types of masseter muscle fibers.Results The induction of CP limited body weight gain, decreased food intake and led to impairment in the morphological and functional parameters of chewing. Moreover, for a comparable amount of food ingested, CP TRI animals grew the most. In addition, supplementation with TRI improved the number of chewing movements, and increased the weight and proportion of type IIB fibers of the masseter in rats subjected to CP.Conclusion These results demonstrate that experimental CP impaired the development of mastication and that TRI supplementation increased masticatory maturation in animals subjected to CP.

Serotonin is essential for eye regeneration in planaria Schmidtea mediterranea

Planaria is an ideal system to study factors involved in regeneration and tissue homeostasis. Little is known about the role of metabolites and small molecules in stem cell maintenance and lineage specification in planarians. Using liquid chromatography and mass spectrometry (LC-MS)-based quantitative metabolomics, we determined the relative levels of metabolites in stem cells, progenitors, and differentiated cells of the planarian Schmidtea mediterranea. Tryptophan and its metabolic product serotonin are significantly enriched in stem cells and progenitor population. Serotonin biosynthesis in these cells is brought about by a noncanonical enzyme, phenylalanine hydroxylase. Knockdown of Smed-pah leads to complete disappearance of eyes in regenerating planaria, while exogenous supply of serotonin and its precursor rescues the eyeless phenotype. Our results demonstrate a key role for serotonin in eye regeneration.

Ion Channel and Neurotransmitter Modulators as Electroceutical Approaches to the Control of Cancer

The activities of individual cells must be tightly coordinated in order to build and maintain complex 3-dimensional body structures during embryogenesis and regeneration. Thus, one way to view cancer is within systems biology as a network disorder affecting the ability of cells to properly interact with a morphodynamic field of instructive signals that keeps proliferation and migration orchestrated toward the anatomical needs of the host or-ganism. One layer of this set of instructive microenvironmental cues is bioelectrical. Voltage gradients among all somatic cells (not just excitable nerve and muscle) control cell behavior, and the ionic coupling of cells into networks via electrochemical synapses allows them to implement tissue-level patterning decisions. These gradients have been increasingly impli-cated in the induction and suppression of tumorigenesis and metastasis, in the emerging links between developmental bioelectricity to the cancer problem. Consistent with the well-known role of neurotransmitter molecules in transducing electrical activity to downstream cascades in the brain, serotonergic signaling has likewise been implicated in cancer. Here, we review these recent data and propose new approaches for manipulating bioelectric and neurotransmitter pathways in cancer biology based on a bioelectric view of cancer. To sup-port this methodology, we present new data on the effects of the SSRI Prozac and its analog (ZINC ID = ZINC06811610) on survival of both cancer (MCF7) and normal (MCF10A) breast cells exposed to these compounds. We found an IC50 concentration (25 μM for Pro-zac and 100 μM for the Prozac analog) at which these compounds inhibited tumor cell sur-vival and proliferation. Additionally, at these concentrations, we did not observe alterations in a non-tumoral cell line. This constitutes a proof-of-concept demonstration for our hy-pothesis that the use of both existing and novel drugs as electroceuticals could serve as an alternative to highly toxic chemotherapy strategies replacing or augmenting them with less toxic alternatives. We believe this new approach forms an exciting roadmap for future bio-medical advances.

Signalling pathways in trophic skeletal development and morphogenesis: Insights from studies on teleost fish

During the development of the vertebrate feeding apparatus, a variety of complicated cellular and molecular processes participate in the formation and integration of individual skeletal elements. The molecular mechanisms regulating the formation of skeletal primordia and their development into specific morphological structures are tightly controlled by a set of interconnected signalling pathways. Some of these pathways, such as Bmp, Hedgehog, Notch and Wnt, are long known for their pivotal roles in craniofacial skeletogenesis. Studies addressing the functional details of their components and downstream targets, the mechanisms of their interactions with other signals as well as their potential roles in adaptive morphological divergence, are currently attracting considerable attention. An increasing number of signalling pathways that had previously been described in different biological contexts have been shown to be important in the regulation of jaw skeletal development and morphogenesis. In this review, I provide an overview of signalling pathways involved in trophic skeletogenesis emphasizing studies of the most species-rich group of vertebrates, the teleost fish, which through their evolutionary history have undergone repeated episodes of spectacular trophic diversification.

Effects of Citalopram on Sutural and Calvarial Cell Processes

The use of selective serotonin reuptake inhibitors (SSRIs) for the treatment of depression during pregnancy is suggested to increase the incidence of craniofacial abnormalities including craniosynostosis. Little is known about this mechanism, however based on previous data we propose a mechanism that affects cell cycle. Excessive proliferation, and reduction in apoptosis may lead to hyperplasia within the suture that may allow for differentiation, bony infiltration, and fusion. Here we utilized in vivo and in vitro analysis to investigate this proposed phenomenon. For in vivo analysis we used C57BL–6 wild-type breeders treated with a clinical dose of citalopram during the third trimester of pregnancy to produce litters exposed to the SSRI citalopram in utero. At post-natal day 15 sutures were harvested from resulting pups and subjected to histomorphometric analysis for proliferation (PCNA) and apoptosis (TUNEL). For in vitro studies, we used mouse calvarial pre-osteoblast cells (MC3T3-E1) to assess proliferation (MTS), apoptosis (Caspase 3/7-activity), and gene expression after exposure to titrated doses of citalopram. In vivo analysis for PCNA suggested segregation of effect by location, with the sagittal suture, showing a statistically significant increase in proliferative response. The coronal suture was not similarly affected, however there was a decrease in apoptotic activity at the dural edge as compared to the periosteal edge. No differences in apoptosis by suture or area due to SSRI exposure were observed. In vitro results suggest citalopram exposure increased proliferation and proliferative gene expression, and decreased apoptosis of the MC3T3-E1 cells. Decreased apoptosis was not confirmed in vivo however, an increase in proliferation without a concomitant increase in apoptosis is still defined as hyperplasia. Thus prenatal SSRI exposure may exert a negative effect on post-natal growth through a hyperplasia effect at the cranial growth sites perhaps leading to clinically significant craniofacial abnormalities.

Tryptophan metabolism, disposition and utilization in pregnancy

Tryptophan (Trp) requirements in pregnancy are several-fold: (1) the need for increased protein synthesis by mother and for fetal growth and development; (2) serotonin (5-HT) for signalling pathways; (3) kynurenic acid (KA) for neuronal protection; (4) quinolinic acid (QA) for NAD(+) synthesis (5) other kynurenines (Ks) for suppressing fetal rejection. These goals could not be achieved if maternal plasma [Trp] is depleted. Although plasma total (free + albumin-bound) Trp is decreased in pregnancy, free Trp is elevated. The above requirements are best expressed in terms of a Trp utilization concept. Briefly, Trp is utilized as follows: (1) In early and mid-pregnancy, emphasis is on increased maternal Trp availability to meet the demand for protein synthesis and fetal development, most probably mediated by maternal liver Trp 2,3-dioxygenase (TDO) inhibition by progesterone and oestrogens. (2) In mid- and late pregnancy, Trp availability is maintained and enhanced by the release of albumin-bound Trp by albumin depletion and non-esterified fatty acid (NEFA) elevation, leading to increased flux of Trp down the K pathway to elevate immunosuppressive Ks. An excessive release of free Trp could undermine pregnancy by abolishing T-cell suppression by Ks. Detailed assessment of parameters of Trp metabolism and disposition and related measures (free and total Trp, albumin, NEFA, K and its metabolites and pro- and anti-inflammatory cytokines in maternal blood and, where appropriate, placental and fetal material) in normal and abnormal pregnancies may establish missing gaps in our knowledge of the Trp status in pregnancy and help identify appropriate intervention strategies.

Effects of treatment with fluoxetine on mandibular development: A morphological study in rats

AIM

To verify whether the use of fluoxetine during gestation and lactation interferes in mandibular bone formation in rats.

METHODS

Twenty-four Wistar rat pups were used and distributed into four groups: CG - control of gestation; CL - control of gestation and lactation; FG - treated with fluoxetine during gestation and FL - treated with fluoxetine during gestation and lactation. At 25 days of life, after anesthesia, perfusion and decapitation, the mandibles were removed. Radiographic, histologic, histometric and polarizing microscopy analyses were performed. Statistical analysis was used considering a level of 5% significance.

RESULT

The FL group compared with its control (CL) was shown to differ statistically from the other groups as regards histometry and radiopacity, revealing a reduction in the inferior cortical thickness, reduction in number of osteocytes, with consequent reduction in radiographic bone density. There was also reduction in the number of osteoblasts in FG.

CONCLUSION

The long-term use of fluoxetine via oral route by pregnant and lactating rats modifies the mandibular bone mass.

Early pregnancy exposure to selective serotonin reuptake inhibitors, risks of major structural malformations, and hypothesized teratogenic mechanisms

INTRODUCTION

Selective serotonin reuptake inhibitors (SSRIs) are commonly used to manage antenatal depression. Hence, the aim of this systematic review is to assess the prevalence of birth defects associated with pregnancy exposure to such agents and summarize the hypothesized teratogenic mechanisms.

AREAS COVERED

Medical literature published in English (1980 - June 2015) was electronically searched to identify all articles reporting an increased prevalence of birth defects associated with prenatal SSRI exposure and hypothesizing teratogenic mechanisms.

EXPERT OPINION

The only recurrent pattern of congenital anomalies associated with antenatal SSRI exposure is heart defects. SSRIs may alter the function of serotonin and related receptors which are involved in the development of the monoamine-dependent cardiac structures. Nevertheless, the magnitude of this increase and, thus, its clinical significance are unclear. Therefore, a cautious approach of using SSRI during pregnancy only in the case of major depressive episodes should be applied. However, this risk should be balanced against the risks associated with the worsening of depressive symptoms, and take into consideration the large number of studies that found no associations between transplacental SSRI exposure and cardiac anomalies. Prenatal ultrasonography and Doppler sonography to detect early cardiac defects are also advisable. Non-pharmacological approaches are preferred for less severe psychiatric disorders.

Serotonin is required for pharyngeal arch morphogenesis in zebrafish

Serotonin (5-HT) is not only a neurotransmitter but also a mediator of developmental processes in vertebrates. In this study, we analyzed the importance of 5-HT during zebrafish development. The expression patterns of three zebrafish tryptophan hydroxylase isoforms (Tph1A, Tph1B, Tph2), the rate-limiting enzymes in 5-HT synthesis, were analyzed and compared to the appearance and distribution of 5-HT. 5-HT was found in the raphe nuclei correlating with tph2 expression and in the pineal gland correlating with tph1a and tph2 expression. tph2 deficient fish generated with antisense morpholino oligonucleotides exhibited morphogenesis defects during pharyngeal arch development. The correct specification of neural crest cells was not affected in tph2 morphants as shown by the expression of early markers, but the survival and differentiation of pharyngeal arch progenitor cells were impaired. An organizing role of 5-HT in pharyngeal arch morphogenesis was suggested by a highly regular pattern of 5-HT positive cells in this tissue. Moreover, the 5-HT2B receptor was expressed in the pharyngeal arches and its pharmacological inhibition also induced defects in pharyngeal arch morphogenesis. These results support an important role of Tph2-derived serotonin as a morphogenetic factor in the development of neural crest derived tissues.

Rate of Chiari I malformation in children of mothers with depression with and without prenatal SSRI exposure

Selective serotonin reuptake inhibitors (SSRIs) are frequently prescribed to pregnant women. Therefore, research on in utero exposure to SSRIs can be helpful in informing patients and clinicians. The aim of this retrospective two-cohort study was to determine whether there is a statistically significant increase in Chiari I malformations (CIM) in children exposed to SSRIs during pregnancy. A total of 33 children whose mothers received a diagnosis of depression and took SSRIs during pregnancy (SSRI-exposed cohort) were matched to 66 children with no history of maternal depression and no SSRI exposure. In addition, 30 children whose mothers received a diagnosis of depression, but did not receive antidepressants during pregnancy (history of maternal depression cohort), were matched to 60 children with no history of maternal depression and no SSRI exposure. Main outcome was presence/absence of CIM on MRI scans at 1 and/or 2 years of age. Scans were reviewed by two independent neuroradiologists who were blind to exposure status. The SSRI-exposed children were significantly more likely to be classified as CIM than comparison children with no history of maternal depression and no SSRI exposure (18% vs 2%, p=0.003, OR estimate 10.32, 95% Wald confidence limits 2.04-102.46). Duration of SSRI exposure, SSRI exposure at conception, and family history of depression increased the risk. The history of maternal depression cohort did not differ from comparison children with no history of maternal depression and no SSRI exposure in occurrence of CIM (7% vs 5%, p=0.75, OR estimate 1.44, 95% Wald confidence limits 0.23-7.85). Replication is needed, as is additional research to clarify whether SSRIs directly impact risk for CIM or whether this relationship is mediated by severity of depressive symptoms during pregnancy. We would discourage clinicians from altering their prescribing practices until such research is available.

Brain as an endocrine source of circulating 5-hydroxytryptamine in ontogenesis in rats

This study was aimed to test the authors' hypothesis stating that the developing brain before the closure of the blood brain barrier (BBB) operates as an endocrine organ that secretes classical neurotransmitters and neuropeptides into the general circulation. 5-Hydroxytryptamine (5-HT) was selected as a marker of brain endocrine activity though it is also secreted by peripheral organs. 5-HT was detected in blood of rats in a biologically active concentration at any studied age, from the 21st embryonic day till the 30th postnatal day. The brain was proven to be a source of circulating 5-HT before the BBB closure by showing that the 5-HT concentration in blood decreased significantly after the inhibition of 5-HT synthesis in the brain of neonates. The 5-HT concentration in blood was not diminished after the BBB closure, apparently due to compensatory increase of 5-HT secretion by peripheral sources. Thus, brain-derived 5-HT is delivered to the general circulation before the BBB closure being potentially capable of providing endocrine regulation of target organs.

The tryptophan utilization concept in pregnancy

The decrease in maternal plasma total (free + albumin-bound) tryptophan (Trp) during the third pregnancy trimester is attributed to induction of indoleamine 2,3-dioxygenase (IDO). When measured, free [Trp] is increased because of albumin depletion and non-esterified fatty acid elevation. The Trp depletion concept in pregnancy is therefore not supported because of incorrect interpretation of changes in Trp disposition and also for not addressing mouse strain differences in Trp-related responses and potential inhibition of Trp transport by the IDO inhibitor 1-methyl tryptophan. Application of the Trp utilization concept in pregnancy offers several physiological advantages favoring fetal development and successful outcome, namely provision of Trp for fetal protein synthesis and growth, serotonin for signaling pathways, kynurenic acid for neuroprotection, quinolinic acid for NAD⁺ synthesis, and other kynurenines for suppression of T cell responses. An excessive increase in Trp availability could compromise pregnancy by undermining T cell suppression, e.g., in pre-eclampsia.

Deletion of serotonin 2B receptor provokes structural alterations of mouse dental tissues

Rampant caries and periodontal diseases occur in patients treated with antidepressants such as serotonin reuptake inhibitors (SRIs; e.g., Prozac) which target the serotonin transporter (SERT). As the serotonin 2B receptor (5HT2BR) regulates SERT functionality and capacity to recognize SRIs, we investigated the potential role of 5HT2BR on dental tissues by exploiting 5HT2BR knockout (KO) mice. Compared to wild-type (WT) mice, several structural differences were identified in the teeth of KO mice. In the molar of KO mice, rod curvatures and twisting were altered compared to WT mice, suggesting involvement of 5HT2BR at early stages of enamel formation. The volume of the KO enamel layer was also reduced, and larger porosities were observed in the prismatic enamel, with smaller crystallite thickness. Crystallite pattern disorganization and occlusal abrasion were enhanced in female KO mice, indicating a sexual dimorphism. In the incisor, no difference was detected in the width of the enamel layer between KO and WT mice; however, enamel maturation differed in absence of 5HT2BR. Specifically, the outer aprismatic enamel border was 1.5- to 2-fold larger in KO compared to WT mice, together with a decreased etching pattern. Finally, although no noticeable difference was observed in dentin, the micro-CT three-dimensional pulp reconstruction evidenced a decrease in both length and width of dentin formation in the root canals of the KO versus WT mice. These data provide evidence that 5HT2BR-mediated signaling pathways are involved in enamel formation and dentinogenesis.

Mesomere-derived glutamate decarboxylase-expressing blastocoelar mesenchyme cells of sea urchin larvae

The ontogenetic origin of blastocoelar glutamate decarboxylase (GAD)-expressing cells (GADCs) in larvae of the sea urchin Hemicentrotus pulcherrimus was elucidated. Whole-mount in situ hybridisation (WISH) detected transcription of the gene that encodes GAD in H. pulcherrimus (Hp-gad) in unfertilised eggs and all blastomeres in morulae. However, at and after the swimming blastula stage, the transcript accumulation was particularly prominent in clumps of ectodermal cells throughout the embryonic surface. During the gastrula stage, the transcripts also accumulated in the endomesoderm and certain blastocoelar cells. Consistent with the increasing number of Hp-gad transcribing cells, immunoblot analysis indicated that the relative abundance of Hp-Gad increased considerably from the early gastrula stage until the prism stage. The expression pattern of GADCs determined by immunohistochemistry was identical to the pattern of Hp-gad transcript accumulation determined using WISH. In early gastrulae, GADCs formed blastocoelar cell aggregates around the blastopore with primary mesenchyme cells. The increase in the number of blastocoelar GADCs was inversely proportional to the number of ectodermal GADCs ranging from a few percent of total GADCs in early gastrulae to 80% in late prism larvae; this depended on ingression of ectodermal GADCs into the blastocoel. Some of the blastocoelar GADCs were fluorescein-positive in the larvae that developed from the 16-cell stage chimeric embryos; these comprised fluorescein-labeled mesomeres and unlabelled macromeres and micromeres. Our finding indicates that some of the blastocoelar GADCs are derived from the mesomeres and thus they are the new group of mesenchyme cells, the tertiary mesenchyme cells.

Association between reported venlafaxine use in early pregnancy and birth defects, national birth defects prevention study, 1997-2007

BACKGROUND

Few epidemiologic studies have investigated the use of venlafaxine (Effexor XR capsules, Product Monograph, Wyeth, Montreal, Canada), an antidepressant used to treat major depression and anxiety disorders in adults, during pregnancy. Our objective was to determine whether use of venlafaxine during pregnancy is associated with specific birth defects.

METHODS

We used data from the National Birth Defects Prevention Study (NBDPS), a population-based, case-control study in the United States. Our analysis included mothers with pregnancies affected by one of 30 selected birth defects (cases) and babies without birth defects (controls) with estimated dates of delivery between 1997 and 2007. Exposure was any reported use of venlafaxine from 1 month preconception through the third month of pregnancy. We calculated adjusted odds ratios (aORs) and 95% Fisher Exact confidence intervals (CIs) for 24 birth defect groups for which at least 400 case mothers were interviewed. Our adjusted analyses controlled for maternal age and race/ethnicity.

RESULTS

Among the 27,045 NBDPS participants who met inclusion criteria, 0.17% (14/8002) of control mothers and 0.40% (77/19,043) of case mothers reported any use of venlafaxine from 1 month preconception through the third month of pregnancy. Statistically significant associations were found for anencephaly, atrial septal defect (ASD) secundum, or ASD not otherwise specified, coarctation of the aorta, cleft palate, and gastroschisis.

CONCLUSIONS

Our data suggest associations between periconceptional use of venlafaxine and some birth defects. However, sample sizes were small, CIs were wide, and additional studies are needed to confirm these results.

Resting potential, oncogene-induced tumorigenesis, and metastasis: the bioelectric basis of cancer in vivo

Cancer may result from localized failure of instructive cues that normally orchestrate cell behaviors toward the patterning needs of the organism. Steady-state gradients of transmembrane voltage (V(mem)) in non-neural cells are instructive, epigenetic signals that regulate pattern formation during embryogenesis and morphostatic repair. Here, we review molecular data on the role of bioelectric cues in cancer and present new findings in the Xenopus laevis model on how the microenvironment's biophysical properties contribute to cancer in vivo. First, we investigated the melanoma-like phenotype arising from serotonergic signaling by 'instructor' cells-a cell population that is able to induce a metastatic phenotype in normal melanocytes. We show that when these instructor cells are depolarized, blood vessel patterning is disrupted in addition to the metastatic phenotype induced in melanocytes. Surprisingly, very few instructor cells need to be depolarized for the hyperpigmentation phenotype to occur; we present a model of antagonistic signaling by serotonin receptors that explains the unusual all-or-none nature of this effect. In addition to the body-wide depolarization-induced metastatic phenotype, we investigated the bioelectrical properties of tumor-like structures induced by canonical oncogenes and cancer-causing compounds. Exposure to carcinogen 4-nitroquinoline 1-oxide (4NQO) induces localized tumors, but has a broad (and variable) effect on the bioelectric properties of the whole body. Tumors induced by oncogenes show aberrantly high sodium content, representing a non-invasive diagnostic modality. Importantly, depolarized transmembrane potential is not only a marker of cancer but is functionally instructive: susceptibility to oncogene-induced tumorigenesis is significantly reduced by forced prior expression of hyperpolarizing ion channels. Importantly, the same effect can be achieved by pharmacological manipulation of endogenous chloride channels, suggesting a strategy for cancer suppression that does not require gene therapy. Together, these data extend our understanding of the recently demonstrated role of transmembrane potential in tumor formation and metastatic cell behavior. V(mem) is an important non-genetic biophysical aspect of the microenvironment that regulates the balance between normally patterned growth and carcinogenesis.

Enamel alterations in serotonin 2B receptor knockout mice

The role of the serotonin 2B receptor (5-HT(2B) R) in enamel formation and mineralization was explored in adult 5HT(2B) R knockout (KO) mice compared with wild-type (WT) mice. In the molar, quantitative data obtained by micro-computed tomography imaging showed that the overall volume of the enamel layer was firmly reduced in KO mice. Defective mineralization was ascertained by energy-dispersive X-ray microanalysis. We also observed, using scanning electron microscopy, that parazones in the KO mice included two or three helicoidally twisted rods within Hunter-Schreger bands, instead of a single rod, as found in the WT mice. Minor disturbances were also detected in the incisors of KO mice. Structural modifications, thinner enamel crystallites, and porosities observed in KO mice indicate that the 5-HT(2B) R-mediated signaling pathways as part of the enamel formation process. These data provide a basis for evaluating the role of 5-HT(2B) R in ameloblast functions. Defects observed in the mineralization and structure of enamel in KO mice highlight that the 5-HT(2B) R interferes with the mechanisms directing amelogenesis.

Chronic exposure to fluoxetine (Prozac) causes developmental delays in Rana pipiens larvae

Selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine, are among the many pharmaceuticals detected in aquatic ecosystems. Although the acute effects of SSRIs on select organisms have been reported, little is understood about the chronic effects of these drugs on amphibians, which are particularly sensitive to environmental pollutants. Serotonin plays important roles in many physiological functions, including a wide array of developmental processes. Exposure to SSRIs during development may cause developmental complications in a variety of organisms, but little is known about the degree of exposure necessary to cause deleterious effects. Here, we sought to gain a better understanding of the effects of SSRIs on amphibian development by use of a combined laboratory and outdoor mesocosm study. Tadpoles in a laboratory setting were exposed to a low (0.029 µg/L) and a high (0.29 µg/L) concentration of the common SSRI fluoxetine from stages 21 and 22 through completion of metamorphosis. Tadpoles in outdoor mesocosms were exposed to fluoxetine concentrations ranging from 0.1 to 0.3 µg/L. Exposed tadpoles in the laboratory showed delayed development compared with controls when stage was assessed throughout the experiment. Control tadpoles also gained weight faster than treatment tadpoles, which may be explained by reduced food intake. Mesocosm tadpoles exhibited similar trends, but no significant differences were detected. These results indicate that ecologically relevant levels of fluoxetine may cause developmental delays in amphibians.

Goldenhar syndrome associated with prenatal maternal Fluoxetine ingestion: Cause or coincidence?

Goldenhar syndrome, also known as oculo-auriculo-vertebral spectrum, is a complex, heterogeneous condition characterized by abnormal prenatal development of facial structures. We present the occurrence of Goldenhar syndrome in an infant born to a woman with a history of prenatal Fluoxetine ingestion throughout her pregnancy. Because this is the first reported case associating maternal Fluoxetine intake with fetal craniofacial malformations, a potential mechanism of injury is discussed. The propositus, a male born from nonconsanguinous parents, had facial asymmetry with right microtia and mandibular hypoplasia; he also had bilateral hypoplastic macula, scoliotic deformity of the thoracic spine, and ventricular septal defect. The mother was under treatment with Fluoxetine 20 mg/day prior to conception and maintained the same dosage throughout her pregnancy. The drug is a selective serotonin re-uptake inhibitor, the most widely prescribed for the treatment of depression. The occurrence of developmental aberrations may be caused by a profound serotonin receptor suppressive state in utero leading to aberrant clinical manifestations of the first and second branchial arches. Despite the very many limitations of case reporting of teratogenic events, it remains an important source of information on which more advanced research is based.

Serotonin and fluoxetine receptors are expressed in enamel organs and LS8 cells and modulate gene expression in LS8 cells

The selective serotonin re-uptake inhibitor (SSRI) fluoxetine is widely used in the treatment of depression in children and fertile women, but its effect on developing tissues has been sparsely investigated. The aim of this study was to investigate if enamel organs and ameloblast-derived cells express serotonin receptors that are affected by peripherally circulating serotonin or fluoxetine. Using RT-PCR and western blot analysis we found that enamel organs from 3-d-old mice and ameloblast-like cells (LS8 cells) express functional serotonin receptors, the rate-limiting enzyme in serotonin synthesis (Thp1), as well as the serotonin transporter (5HTT), indicating that enamel organs and ameloblasts are able to respond to serotonin and regulate serotonin availability. Fluoxetine and serotonin enhanced the alkaline phosphatase activity in the cell culture medium from cultured LS8 cells, whereas the expression of enamelin (Enam), amelogenin (Amel), and matrix metalloproteinase-20 (MMP-20) were all significantly down-regulated. The secretion of vascular endothelial growth factor (VEGF), monocyte chemotactic protein 1 (MCP-1), and interferon-inducible protein 10 (IP-10) was also reduced compared with controls. In conclusion, enamel organs and ameloblast-like cells express functional serotonin receptors. Reduced transcription of enamel proteins and secretion of vascular factors may indicate possible adverse effects of fluoxetine on amelogenesis.

Serotonin 2B receptor signaling is required for craniofacial morphogenesis and jaw joint formation in Xenopus

Serotonin (5-HT) is a neuromodulator that plays many different roles in adult and embryonic life. Among the 5-HT receptors, 5-HT2B is one of the key mediators of 5-HT functions during development. We used Xenopus laevis as a model system to further investigate the role of 5-HT2B in embryogenesis, focusing on craniofacial development. By means of gene gain- and loss-of-function approaches and tissue transplantation assays, we demonstrated that 5-HT2B modulates, in a cell-autonomous manner, postmigratory skeletogenic cranial neural crest cell (NCC) behavior without altering early steps of cranial NCC development and migration. 5-HT2B overexpression induced the formation of an ectopic visceral skeletal element and altered the dorsoventral patterning of the branchial arches. Loss-of-function experiments revealed that 5-HT2B signaling is necessary for jaw joint formation and for shaping the mandibular arch skeletal elements. In particular, 5-HT2B signaling is required to define and sustain the Xbap expression necessary for jaw joint formation. To shed light on the molecular identity of the transduction pathway acting downstream of 5-HT2B, we analyzed the function of phospholipase C beta 3 (PLC) in Xenopus development and showed that PLC is the effector of 5-HT2B during craniofacial development. Our results unveiled an unsuspected role of 5-HT2B in craniofacial development and contribute to our understanding of the interactive network of patterning signals that is involved in the development and evolution of the vertebrate mandibular arch.

Morphological analysis of the enamel organ in rats treated with fluoxetine

PURPOSE

Previous studies have evaluated the presence of serotonin in the dental epithelia and mesenchyme during odontogenesis, suggesting its participation in tooth development.

MATERIALS AND METHODS

Here, we used fluoxetine, a selective serotonin re-uptake inhibitor, at a dose of 10 mg/kg, administered for 20 days during pregnancy in 12 Wistar rats to examine the influence of this drug on the development of the enamel organ of the upper first molars of rat fetuses at 17 days of intra-uterine life (i.u.l.), and at one, five and ten days postpartum. The pregnant rats were anesthetized with xylazine at 10 mg/kg and ketamine at 25 mg/kg. The fetuses were removed and beheaded; their jaws were removed, and the upper jaws were exposed. The tissues were fixed in Bouin's fixative, decalcified in 5% nitric acid for 4 - 12 h, conventionally processed for microscopy, and embedded in paraffin. Serial sections of approximately 5 mum were obtained and stained with hematoxylin and eosin, as well as periodic acid-Schiff.

RESULTS AND CONCLUSION

Morphological analysis showed no structural changes in the experimental group compared to the controls, suggesting that, at the dose used, fluoxetine does not interfere with serotonin-mediated development of the enamel organ or the process of amelogenesis.

The serotonin 5-HT2B receptor controls bone mass via osteoblast recruitment and proliferation

The monoamine serotonin (5-HT), a well-known neurotransmitter, is also important in peripheral tissues. Several studies have suggested that 5-HT is involved in bone metabolism. Starting from our original observation of increased 5-HT(2B) receptor (5-HT(2B)R) expression during in vitro osteoblast differentiation, we investigated a putative bone phenotype in vivo in 5-HT(2B)R knockout mice. Of interest, 5-HT(2B)R mutant female mice displayed reduced bone density that was significant from age 4 months and had intensified by 12 and 18 months. This histomorphometrically confirmed osteopenia seems to be due to reduced bone formation because 1) the alkaline phosphatase-positive colony-forming unit capacity of bone marrow precursors was markedly reduced in the 5-HT(2B)R mutant mice from 4 to 12 months of age, 2) ex vivo primary osteoblasts from mutant mice exhibited reduced proliferation and delayed differentiation, and 3) calcium incorporation was markedly reduced in osteoblasts after 5-HT(2B)R depletion (produced genetically or by pharmacological inactivation). These findings support the hypothesis that the 5-HT(2B)R receptor facilitates osteoblast recruitment and proliferation and that its absence leads to osteopenia that worsens with age. We show here, for the first time, that the 5-HT(2B)R receptor is a physiological mediator of 5-HT in bone formation and, potentially, in the onset of osteoporosis in aging women.

Fluoxetine treatment increases trabecular bone formation in mice

Mounting evidence exists for the operation of a functional serotonin (5-HT) system in osteoclasts and osteoblasts, which involves both receptor activation and 5-HT reuptake. In previous work we showed that the serotonin transporter (5-HTT) is expressed in osteoclasts and that its activity is required by for osteoclast differentiation in vitro. The purpose of the current study was to determine the effect of treatment with fluoxetine, a specific serotonin reuptake inhibitor, on bone metabolism in vivo. Systemic administration of fluoxetine to Swiss-Webster mice for 6 weeks resulted in increased trabecular BV and BV/TV in femurs and vertebrae as determined by micro-computed tomography (microCT). This correlated with an increase in trabecular number, connectivity, and decreased trabecular spacing. Fluoxetine treatment also resulted in increased volume in vertebral trabecular bone. However, fluoxetine-treated mice were not protected against bone loss after ovariectomy, suggesting that its anabolic effect requires the presence of estrogen. The effect of blocking the 5-HTT on bone loss following an LPS-mediated inflammatory challenge was also investigated. Subcutaneous injections of LPS over the calvariae of Swiss-Webster mice for 5 days resulted in increased numbers of osteoclasts and net bone loss, whereas new bone formation and a net gain in bone mass was seen when LPS was given together with fluoxetine. We conclude that fluoxetine treatment in vivo leads to increased bone mass under normal physiologic or inflammatory conditions, but does not prevent bone loss associated with estrogen deficiency. These data suggest that commonly used anti-depressive agents may affect bone mass.

Long-term fluoxetine administration does not result in major changes in bone architecture and strength in growing rats

Many studies have indicated that serotonin and its transporter play a role in bone metabolism. In this study we investigated the effect of selective serotonin re-uptake inhibitor (SSRI), fluoxetine (Prozac) on bone architecture and quality in growing female rats. We therefore administrated rats with clinically relevant doses of fluoxetine for a period of 6 months. DXA scans were performed during the treatment period in order to follow parameters as body weight, fat percentage and BMD. After 6 months of treatment, femurs were used to analyze bone architecture and bone strength, by means of microCT scans and three-point bending assays, respectively. We found a slightly diminished bone quality, reflected in a lower bone tissue strength, which was compensated by changes in bone geometry. As leptin and adiponectin could be possible factors in the serotonergic regulation of bone metabolism, we also determined the levels of these factors in plasma samples of all animals. Leptin and adiponectin levels were not different between the control group and fluoxetine-treated group, indicating that these factors were not involved in the observed changes in bone geometry and quality.

Immunohistochemical localization of aromatic l-amino acid decarboxylase in mouse taste buds and developing taste papillae

Aromatic L-amino acid decarboxylase (AADC) catalyses the decarboxylation of all aromatic L-amino acids. In mammals, AADC is expressed in many tissues besides the nervous system, and is associated with additional regulatory roles of dopamine and serotonin in a wide range of tissues. We examined the expression of AADC by using reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. RT-PCR analysis showed that mRNA of AADC was detected in the taste bud-containing epithelium of the circumvallate papilla of mice. By immunohistochemical analyses, AADC was detected in a subset of taste bud cells of fungiform, foliate, and circumvallate papillae. Double-label studies showed that AADC colocalized with serotonin, NCAM, PLCbeta2, and PGP9.5. On the other hand, AADC never colocalized with alpha-gustducin. Our results of double staining with AADC and taste cell markers indicate that only the type III cells could convert 5-hydroxytryptophan (5-HTP) to serotonin within taste buds. Taken together with previous studies, the properties of the type III cell of taste buds exactly fit into the APUD (amine and amine precursor uptake and decarboxylation) cell scheme. Furthermore, in the developing circumvallate papilla, AADC are first detected in a small number of papillary epithelial cells at E14.5. By E18.5, AADC-positive epithelial cells also express PGP9.5, which is one of marker of taste cells, and these cells have been contacted by developing nerve fibers. These results suggest that AADC expression begins at early stages of taste bud cell differentiation, and biogenic amines may act on taste bud differentiation of tongue epithelial cells, and further may regulate innervation of taste bud progenitor cells.

Maternal serotonin is crucial for murine embryonic development

The early appearance of serotonin and its receptors during prenatal development, together with the many effects serotonin exerts during CNS morphogenesis, strongly suggest that serotonin influences the development and maturation of the mammalian brain before it becomes a neuromodulator/neurotransmitter. Sites of early serotonin biosynthesis, however, have not been detected in mouse embryos or extraembryonic structures, suggesting that the main source of serotonin could be of maternal origin. This hypothesis was tested by using knockout mice lacking the tph1 gene, which is responsible for the synthesis of peripheral serotonin. Genetic crosses were performed to compare the phenotype of pups born from homozygous and heterozygous mothers. Observations provide the first clear evidence that (i) maternal serotonin is involved in the control of morphogenesis during developmental stages that precede the appearance of serotonergic neurons and (ii) serotonin is critical for normal murine development. Most strikingly, the phenotype of tph1-/- embryos depends more on the maternal genotype than on that of the concepti. Consideration of the maternal genotype may thus help to clarify the influence of other genes in complex diseases, such as mental illness.

Pregnancy outcomes following exposure to serotonin reuptake inhibitors: a meta-analysis of clinical trials

Serotonin reuptake inhibitors (SRIs) are extensively used in management of clinical depression. Reports vary about the risk of these drugs during pregnancy. To determine the risk of exposure to SRIs, we pooled data from multiple clinical studies that investigated obstetrical outcomes in women exposed to this group of drugs during pregnancy. Studies were identified by search of PUBMED, OVID, and SCOPUS databases and the data were derived from 1990 to 2005 (August). Types of outcome investigated were spontaneous abortion, major malformations, cardiovascular malformations, and minor malformations. The criteria for inclusion of studies in this meta-analysis were exposure of women to any therapeutic dosage of SRI (citalopram, fluoxetine, fluvoxamine, paroxetine, sertraline) during pregnancy. Our results find that SRIs do not increase the risk of major, cardiovascular and minor malformations but do increase the risk of spontaneous abortion significantly.

Cellular pattern formation during retinal regeneration: a role for homotypic control of cell fate acquisition

A dominant mechanism of cellular patterning in the growing fish retina is control of cell fate acquisition by negative feedback signals arising from differentiated cells. We tested the ability of a computational model of this pattern formation mechanism to simulate cellular patterns in regenerated goldfish retina. The model successfully simulated quantitative features of in vivo regenerated patterns, indicating that regenerating retina has access to and utilizes patterning mechanisms that are operational during normal growth. The atypical patterns of regenerated retina could arise in part from regenerative progenitors that, compared to normal growth progenitors, are less responsive to the feedback patterning signals.