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PubMed2006

Positive selection on the nonhomologous end-joining factor Cernunnos-XLF in the human lineage.

BACKGROUND: Cernunnos-XLF is a nonhomologous end-joining factor that is mutated in patients with a rare immunodeficiency with microcephaly. Several other microcephaly-associated genes such as ASPM and microcephalin experienced recent adaptive evolution apparently linked to brain size expansion in humans. In this study we investigated whether Cernunnos-XLF experienced similar positive selection during human evolution. RESULTS: We obtained or reconstructed full-length coding sequences of chimpanzee, rhesus macaque, canine, and bovine Cernunnos-XLF orthologs from sequence databases and sequence trace archives. Comparison of coding sequences revealed an excess of nonsynonymous substitutions consistent with positive selection on Cernunnos-XLF in the human lineage. The hotspots of adaptive evolution are concentrated around a specific structural domain, whose analogue in the structurally similar XRCC4 protein is involved in binding of another nonhomologous end-joining factor, DNA ligase IV. CONCLUSION: Cernunnos-XLF is a microcephaly-associated locus newly identified to be under adaptive evolution in humans, and possibly played a role in human brain expansion. We speculate that Cernunnos-XLF may have contributed to the increased number of brain cells in humans by efficient double strand break repair, which helps to prevent frequent apoptosis of neuronal progenitors and aids mitotic cell cycle progression. REVIEWERS: This article was reviewed by Chris Ponting and Richard Emes (nominated by Chris Ponting), Kateryna Makova, Gáspár Jékely and Eugene V. Koonin.

Journal Article↗

PubMed1999

Prenatal detection and mapping of a distal 8p deletion associated with congenital heart disease.

We report the prenatal diagnosis, at 18 weeks' gestational age of a del(8)(p23.1-->pter) in a fetus with an atrio-ventricular canal, persistent left superior vena cava and hypoplastic right ventricle detected by sonographic imaging. We further refine the breakpoints associated with this defect using fluorescent in situ hybridization analysis (FISH). Our findings correlate with recent reports of the localization and importance of GATA4 (a zinc finger transcription factor) in cardiac development. Though microcephaly, mental retardation and typical behavioural features are well described in various deletions in 8p, the absence of notable microcephaly in this case raises the possibility for a separate genetic aetiology for some of these features. Indeed, primary autosomal recessive microcephaly (MCPH1) was recently mapped to a nearby region and may be the cause for this frequent observation in some cases of 8p deletions. These observations illustrate the role of FISH in prenatal diagnosis and refinement of chromosomal breakpoints. In addition, mappings of loci significant for cardiac development are presented. Our findings suggest that some features of the 8p deletion syndrome may ultimately be uncoupled from one another, and underscore the need for further study of this region of chromosome 8, in order to achieve adequate information for genetic counselling.

Adult↗

PubMed1992

Epilepsy, antiepileptic drugs, and malformations in children of women with epilepsy: a French prospective cohort study.

We conducted a prospective study of teratogenic effects of antiepileptic drugs (AEDs) in pregnant women with epilepsy in southeast France, comparing malformation rates with those collected by a birth defects registry. We evaluated isolated microcephalies separately. Malformations were seen in 7% of infants of mothers with epilepsy (IME) and in 1.36% of the general population. No significant relationship was found between type and severity of epilepsy and occurrence of malformations or isolated microcephaly. Valproate and phenytoin were the most teratogenic (all malformations). None of the malformations observed in IME whose mothers received valproate, phenytoin, or phenobarbital was seen in IME not exposed to the respective AEDs. Phenytoin plus phenobarbital was more teratogenic than phenobarbital alone. Benzodiazepines, prescribed only in combinations, had a borderline, nonspecific effect on microcephaly.

Abnormalities, Drug-Induced↗

PubMed1993

[Familial agenesis of the corpus callosum: a new form].

BACKGROUND. Agenesis of the corpus callosum is generally associated with other developmental defects of the cerebrum. Some familial cases have been reported. CASES REPORTS Case n. 1. A 6 year-old girl was examined because of developmental retardation, first noted at the age of 3 months. There was no consanguinity but 2 girls, cousins of the father, died at 17 and 18 years with the same clinical presentation. Our patient had seizures at 4 years. At examination, she had microcephaly, dilated unreactive pupils, and generalized hypotonia. Her IQ was 15. Funduscopic examination showed optic atrophy and visual evoked potentials were abnormal. The EEG showed spike-wave discharges and the CT scan showed agenesis of the corpus callosum plus heterotopias of the grey matter and brain atrophy. The child died at 12 years of age. Case n. 2. At 15 month-old girl, sister of case n. 1, had shown developmental retardation since the age of 4 months. She had microcephaly, dilated unreactive pupils, generalized hypotonia. Her IQ was 20. She also had optic atrophy, abnormal visual evoked potentials and a hypsarrhythmic pattern on EEG. The CT scan showed agenesis of corpus callosum plus heterotopias of the grey matter and brain atrophy. She died at the age of 10 years. Case n. 3. This boy, brother of cases 1 and 2, was examined on the first day of life. He had microcephaly and some spike-wave discharges on EEG. The CT scan and MRI showed agenesis of the corpus callosum. He had generalized hypotonia at 5 months with an IQ of 30; he suffered from seizures at 18 months. CONCLUSIONS. This agenesis of the corpus callosum seems to have an autosomal recessive inheritance. The associated developmental defects are different from those previously reported, suggesting that these cases represent a new form of corpus callosum lack.

Abnormalities, Multiple↗

PubMed1998

Strong variable clinical presentation in 3 patients with 7q terminal deletion.

We report 3 patients with a 7q terminal deletion. The first, a 7 weeks old female, with a de novo 7q36-->qter deletion, was microcephalic and had a partial hypoplasia of the corpus callosum on the MRI-scan of the brain. The second, a 3 months old male, showed microcephaly, disproportionate growth retardation, truncal obesity and facial dysmorfism giving the clinical impression of a "microcephalic primordial dwarfism (osteodysplastic type)". At the age of 6 months he had developed a single maxillary central incisor suggesting a minimal form of holoprosencephaly (HPE). Additional FISH-studies showed a 7q36.1-->qter deletion, as the unbalanced product of a t(5;7)(q35.2;q36.1)pat. The de novo 7q36-->qter deletion in the third patient, a 5 years old female, was associated with borderline intelligence, mild microcephaly, small midface, choanal narrowing and a single maxillary central incisor as a minimal form of HPE. CT- and MRI-scan of the brain were normal. In these 3 patients extensive FISH analysis was performed to investigate the possible involvement of the HPE gene region on chromosome 7q36. The target gene for HPE, the Sonic hedgehog gene (SHH) as well as several other genes important for normal brain development (En2;HOX1,HTR5A) were found to be deleted in all three patients. Our findings stress the importance of 7q36 microdeletion studies in patients with even minimal signs of HPE, as relative microcephaly with small midface (choanal narrowing), agenesis/hypoplasia of the corpus callosum/septum pellucidum, thalamic fusion or a single maxillary central incisor.

Abnormalities, Multiple↗

PubMed2023

H4C5 missense variant leads to a neurodevelopmental phenotype overlapping with Angelman syndrome.

Recurrent de novo missense variants in H4 histone genes have recently been associated with a novel neurodevelopmental syndrome that is characterized by intellectual disability and developmental delay as well as more variable findings that include short stature, microcephaly, and facial dysmorphisms. A 4-year-old male with autism, developmental delay, microcephaly, and a happy demeanor underwent evaluation through the Undiagnosed Disease Network. He was clinically suspected to have Angelman syndrome; however, molecular testing was negative. Genome sequencing identified the H4 histone gene variant H4C5 NM_003545.4: c.295T>C, p.Tyr99His, which parental testing confirmed to be de novo. The variant met criteria for a likely pathogenic classification and is one of the seven known disease-causing missense variants in H4C5. A comparison of our proband's findings to the initial description of the H4-associated neurodevelopmental syndrome demonstrates that his phenotype closely matches the spectrum of those reported among the 29 affected individuals. As such, this report corroborates the delineation of neurodevelopmental syndrome caused by de novo missense H4 gene variants. Moreover, it suggests that cases of clinically suspected Angelman syndrome without molecular confirmation should undergo exome or genome sequencing, as novel neurodevelopmental syndromes with phenotypes overlapping with Angelman continue to be discovered.

Male↗

PubMed1989

Perinatal outcome of infants exposed to cocaine and/or heroin in utero.

While cocaine is now used much more frequently than heroin by women of childbearing age, we have found that a significant number of mothers have abused both drugs during their pregnancy. We studied 86 infants who were born to women with a history of cocaine and/or heroin use during pregnancy. The newborns were observed over a 5-day hospital period using a standardized abstinence scoring system and urine drug screening of both mother and infant. Of these, 35 had maternal and/or newborn urine test results that were positive for cocaine only (cocaine group), 14 that were positive for heroin only (heroin group), 17 that were positive for both cocaine and heroin (cocaine/heroin group), and 20 that were negative for both, although the mothers admitted to cocaine use during their pregnancy (cocaine history group). In approximately half of the mother/infant pairs, the results of the urine drug tests were discordant. Microcephaly and growth retardation occurred most frequently in the infants in the cocaine group (17% and 27%, respectively). Microcephaly was also found to be significant in the infants in the cocaine/heroin group. Signs of drug withdrawal occurred in all four drug-exposed groups. Mild withdrawal occurred in 26% of infants in the cocaine group, 21% of the infants in the heroin group, 47% of the infants in the cocaine/heroin group, and in 30% of the infants in the cocaine history group. Withdrawal requiring treatment occurred in 6% of the infants in the cocaine group, 14% of the infants in the heroin group, 35% of infants in the cocaine/heroin group, and 5% of the infants in the cocaine history group. The use of heroin with cocaine has a synergistic effect on the behavior of the newborn.

Cocaine↗

PubMed1996

Linear disruption of umbilical cord: a rare anomaly of the cord associated with acute fetal distress and perinatal death/profound psychomotor retardation.

We report on a non-malformed child with severe microcephaly and profound psychomotor delay. Review of the delivery/birth records documented descriptions consistent with linear disruption of the umbilical cord. This rare anomaly typically leads to acute fetal distress and perinatal death. Severe microcephaly and psychomotor delay without other anomalies should prompt a careful review of the delivery/birth records to search for umbilical cord descriptions consistent with this diagnosis.

Child, Preschool↗

PubMed1997

A recognisable behavioural phenotype associated with terminal deletions of the short arm of chromosome 8.

We report the clinical findings in 5 patients with a terminal deletion of the short arm of chromosome 8. Mild developmental delay was constantly present, in association with microcephaly in 4 of 5 patients. Facial anomalies were mild or absent. A congenital heart defect was present in 3 patients: an atrioventricular septal defect (AVSD) in 2 and an atrial septal defect type II (ASDII) with pulmonary stenosis in one. A highly similar pattern of behavioural difficulties was present in the 3 older children (8-11 years), with outbursts of aggressiveness and destructive behaviour. Follow-up in one patient showed that at the age of 16 years, these behavioural problems had largely disappeared. This observation suggests that in addition to mental retardation, microcephaly, congenital heart defect (typically AVSD), a terminal deletion of chromosome 8p may be associated with a characteristic behavioural phenotype during childhood.

Behavioral Symptoms↗

PubMed1999

Say syndrome: report of a familial case.

We describe a new case of Say syndrome. This syndrome is an autosomal dominant condition characterized by cleft palate, short stature of prenatal onset, large protruding ears and microcephaly, delayed bone age, and renal anomalies. The first report was in 1975 by Say et al. in three generations of a family. Three additional reports of isolated cases were published. Our propositus is a 12-month-old boy with the cardinal signs of the syndrome whose mother has only microcephaly. To our knowledge this is the second familial report with evidence of highly variable expressivity. The occurrence of renal anomalies in a son of a normal sister of his mother suggests incomplete penetrance.

Abnormalities, Multiple↗

PubMed1996

Maternal phenylketonuria: a metabolic teratogen.

The maternal phenylketonuria (PKU) syndrome refers to the teratogenic effects of PKU during pregnancy. These effects include mental retardation, microcephaly, congenital heart disease, and intrauterine growth retardation. In untreated pregnancies wherein the mother has classic PKU with a blood phenylalanine level > or = 1,200 microM (20 mg/dl), the frequencies of these abnormalities in offspring are exceedingly high, approaching 75-90% for microcephaly and mental retardation and 15% for congenital heart disease. There is a dose response relationship with progressively lower frequencies of these abnormalities at lower phenylalanine levels, both in the pregnancies of women with variants of PKU and in treated classic PKU pregnancies. The pathogenesis of this syndrome is unknown; it may be related to inhibition by phenylalanine of large neutral amino acid transport across the placenta or to direct toxicity of phenylalanine and/or a phenylalanine metabolite in certain fetal organs. A mouse model for PKU now exists, and studies of maternal PKU in this model are in progress. The treatment of maternal PKU consists of biochemical control through a phenylalanine restricted diet during pregnancy. The best results are obtained with diet initiation before conception or no later than the earliest weeks of pregnancy. Women with PKU and their families require much psychosocial support to meet the strict requirements of a maternal PKU pregnancy, including compliance with a difficult diet. With such compliance, however, it seems that bearing normal or near normal offspring is possible.

Abnormalities, Multiple↗

PubMed2002

High risk of malignancy in mosaic variegated aneuploidy syndrome.

Fourteen cases of mosaic variegated aneuploidy (MVA) syndrome have been reported in the last 10 years. The phenotype of this rare condition has been quite consistent: severe microcephaly, growth deficiency, mild physical anomalies, and mental retardation. We describe here a young boy in whom MVA syndrome is associated to myelodysplasia with a monosomy 7 bone marrow clone. At the age of 3 years, myelodysplasia progressed to an acute lymphoblastic leukemia, and the patient died soon after. Several syndromes with short stature and severe microcephaly, such as the Seckel and Nijmegen syndromes, comprise hematological findings and chromosome instability. However, chromosome instability was not confirmed in our patient. MVA with hematological findings has not been reported before, but 3 patients of 14 (21%) have developed a malignancy (rhabdomyosarcoma, acute lymphoblastic leukemia, and nephroblastoma). Therefore, we propose that MVA is a condition predisposing to neoplasia.

Abnormalities, Multiple↗

PubMed2002

Mosaic variegated aneuploidy with growth hormone deficiency and congenital heart defects.

We describe a 12-year-old boy with mosaic variegated aneuploidy (MVA), subnormal response to growth hormone (GH) stimulation testing, and short stature. In addition to features more commonly described in MVA such as microcephaly, cognitive deficits, and certain facial features, he also has features not commonly reported in MVA, including short limb segments, epidermoid cysts, ventricular septal defect, and subaortic stenosis. Chromosomal analysis revealed hyperdiploid chromosome numbers ranging from 47 to 70; modal number 50, in 24% of the metaphases. This case demonstrates that although the phenotype of MVA almost always includes growth failure, microcephaly, and mental retardation, additional features may vary greatly across individuals. His clinical features and course suggest that in addition to GH deficiency, he may have an intrinsic inability of the growth plate to respond to growth hormone.

Abnormalities, Multiple↗

PubMed1981

Cohen syndrome: further delineation and inheritance.

Four sibs, 2 males and 2 females, were found to have the Cohen syndrome. All had moderate mental retardation, microcephaly, hypotonia, and narrow hands and feet with elongated fingers and toes; 3 were short of stature (2.0-3.5 SD below the mean) with weight between 10th and 50th centile and truncal obesity. Most of the facial characteristics of the syndrome were present: exotropia, prominent ears, short philtrum, and high nasal bridge. Each manifestation varied in severity from one sib to the other. The younger girl also had rheumatoid arthritis. Mild delay of puberty was described in 3 of the sibs. However, one of them has delivered a male infant with normal appearance whose psychomotor development has been normal (as of 9 months). No endocrine problems were documented in the sibship. All patients had normal chromosomes. The data on this sibship support the hypothesis of autosomal recessive inheritance of the Cohen syndrome. Microcephaly and short stature should be stressed as frequent manifestations of the syndrome. The variable expressivity, even among sibs, may be responsible for the paucity of reports on the mildest forms of the Cohen syndrome.

Adolescent↗

PubMed1985

X-linked syndrome of branchial arch and other defects.

We report on two brothers and their maternal first cousin who have branchial arch defects and other anomalies. Similar physical findings in all three include microcephaly, downslanting palpebral fissures, highly arched palate, apparently lowset, protruding ears, bilateral hearing loss, slightly webbed neck, and mild short stature. In addition, two boys had cryptorchidism, and one had subvalvar pulmonic stenosis and body asymmetry. We suggest that these cousins have an X-linked syndrome of which branchial arch defects are a component. Other pleiotropic manifestations of the mutant gene include microcephaly and cryptorchidism; body asymmetry and relatively short stature may be components as well.

Abnormalities, Multiple↗

PubMed1987

Wrinkly skin syndrome: phenotype and additional manifestations.

The wrinkly skin syndrome is an autosomal recessive disorder characterized by wrinkling of the skin of the dorsum of the hands and feet, decreased elastic recoil of the skin, an increased number of palmar and plantar creases, multiple musculoskeletal abnormalities, microcephaly, and mental retardation. Our patient is characteristic of the syndrome as previously described, and confirms the presence of mental retardation and microcephaly as component manifestations, with the additional findings of connective tissue abnormalities evidenced by an atrial septal aneurysm.

Abnormalities, Multiple↗

PubMed1990

Loss of the 3p25.3 band is critical in the manifestation of del(3p) syndrome: karyotype-phenotype correlation in cases with deficiency of the distal portion of the short arm of chromosome 3.

Two patients with monosomy for the distal portion of the short arm of chromosome 3 are described. Chromosome analysis on prometaphase cells demonstrated a karyotype of 46,XX,del(3) (p25.3) in one patient and 46,XX,r(3)(p26.1q29) in the other. The former patient showed characteristic clinical manifestations of the 3p- syndrome, including growth failure, mental retardation, microcephaly with a flat occiput, triangular face, synophrys, blepharoptosis, hypertelorism, broad and flat nose, long philtrum, down-turned mouth, micrognathia, apparently lowset and malformed ears, fingers abnormalities, and deafness. The latter patient had a nonspecific phenotype with mental retardation, growth failure and microcephaly. Karyotype-phenotype comparisons in the present cases and 16 previously reported cases with deficiency of the distal portion of 3p suggests that deficiency of the 3p25.3 band is critical to produce the main clinical manifestations of the del(3p) syndrome.

Chromosome Deletion↗

PubMed1992

Stable ring chromosome 21: molecular and clinical definition of the lesion.

Ring chromosome 21 results in deletions of chromosome 21. We report on a cytogenetic and molecular analysis of a 4-generation family segregating a stable ring chromosome 21 in 4 relatives. To investigate the molecular structure of the ring chromosome, we have analyzed the DNAs of the transmitted ring in a mother and her daughter. The daughter presented at the age of 2 years with severe growth retardation and microcephaly, whereas her mother had microcephaly but normal intelligence. High resolution chromosome analysis of both cases showed the ring chromosome to be r(21)(p13q22) resulting in deletions of 21p and 21q22. The molecular content of the ring chromosome was determined using quantitative Southern blot analyses of 5 random DNA sequences and 4 expressed genes assigned to chromosome 21 and mapping in the region of q22.3. We have shown that collagen type VI, alpha 2 (COL6A2,) S100 protein, beta polypeptide (neural), (S100B), and D21S44 are present in only one copy in both ring carriers, while CRYA1, CBS, D21S43, D21S42, D21S41, and D21S39 are present in two copies. These data and the breakpoints defining the deletion in these patients show that deletion of COL6A2 and S100B is compatible with normal function and confirm the physical map of 21q22.3 by placing COL6A2, S100B, and D21S44 in very distal 21q22.3. Patients with such small deletions provide unique models for understanding the biological and clinical significance of aneuploidy for specific expressed genes.

Adult↗