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Congenital microcephaly (MCPH) is a neurodevelopmental disease associated to mutations in genes encoding proteins involved in centrosomal and chromosomal dynamics during mitosis. Detailed MCPH pathogenesis at the cellular level is still elusive given the diversity of MCPH genes and lack of comparative in vivo studies. By generating a series of CRISPR/Cas9-mediated genetic knockouts we report here that, whereas defects in spindle pole proteins (ASPM, MCPH5) result in mild microcephaly during development, lack of centrosome (CDK5RAP2, MCPH3) or centriole (CEP135, MCPH8) regulators induces delayed chromosome segregation and chromosomal instability in neural progenitors (NPs). Our novel mouse model of MCPH8 suggests that Cep135 deficiency results in centriole duplication, TP53 activation and cell death of NPs. Trp53 ablation in a Cep135-deficient background prevents cell death, but not microcephaly, and leads to subcortical heterotopias, a malformation seen in MCPH8 patients. These results suggest that microcephaly in some MCPH patients can arise from the lack of adaptation to centriole defects in NPs and may lead to architectural defects if chromosomally unstable cells are not eliminated during brain development.

This study analyzed possible associations between the trimester of maternal Zika virus infection (ZIKV) in pregnancy, severity of brain computed tomography (CT) findings and the presence of microcephaly at birth in children with Congenital Zika Syndrome (CZS). It was an analytical study in a cohort of children with CZS. Symptoms of maternal infection were dichotomized into the 1st trimester of pregnancy and other trimesters. Head circumference (HC) at birth was used to calculate the z-score. Mild microcephaly was defined as HC between 2 and ≥3 standard deviations (SD) below the mean for each gestational age and sex, and severe microcephaly when HC

Introductory paragraphUntil recently missense germ-line mutations inACTB, encoding the ubiquitously expressed β-cytoplasmic actin (CYA), were exclusively associated with Baraitser-Winter Cerebrofrontofacial syndrome (BWCFF), a complex developmental disorder1,2. Here, we report six patients with previously undescribed heterozygous variants clustered in the 3’-coding region ofACTB. These patients present with clinical features different from BWCFF, including thrombocytopenia, microcephaly, and mild developmental disability. Patient derived cells are morphologically and functionally distinct from controls. Assessment of cytoskeletal constituents identified a discrete filament population altered in these cells, which comprises force generating and transmitting actin binding proteins (ABP) known to be associated with thrombocytopenia3–8.In silicomodelling and molecular dynamics (MD)-simulations support altered interactions between these ABP and mutant β-CYA. Our results describe a new clinical syndrome associated withACTBmutations with a distinct genotype-phenotype correlation, identify a cytoskeletal protein interaction network crucial for thrombopoiesis, and provide support for the hypomorphic nature of these actinopathy mutations.

Intellectual disability (ID) has an estimated prevalence of 1.5–2%. In most affected individuals, its genetic basis remains unclear. Whole exome sequencing (WES) studies have identified a multitude of novel causative gene defects and have shown that a large proportion of sporadic ID cases results from de novo mutations. Here, we present two unrelated individuals with similar clinical features and deleterious de novo variants in FBXO11 detected by WES. Individual 1, a 14-year-old boy, has mild ID as well as mild microcephaly, corrected cleft lip and alveolus, hyperkinetic disorder, mild brain atrophy and minor facial dysmorphism. WES detected a heterozygous de novo 1 bp insertion in the splice donor site of exon 3. Individual 2, a 3-year-old boy, showed ID and pre- and postnatal growth retardation, postnatal mild microcephaly, hyperkinetic and restless behaviour, as well as mild dysmorphism. WES detected a heterozygous de novo frameshift mutation. While ten individuals with ID and de novo variants in FBXO11 have been reported as part of larger studies, only one of the reports has some additional clinical data. Interestingly, the latter individual carries the identical mutation as our individual 2 and also displays ID, intrauterine growth retardation, microcephaly, behavioural anomalies, and dysmorphisms. Thus, we confirm deleterious de novo mutations in FBXO11 as a cause of ID and start the delineation of the associated clinical picture which may also comprise postnatal microcephaly or borderline small head size and behavioural anomalies.

We report a case of an unbalanced cryptic telomeric translocation 46,XY,der(17),t(9;17)(q34.3;p13.3) in a boy with dysmorphic features and developmental delay. The proband had intrauterine growth retardation, postnatal short stature, and mild microcephaly. Magnetic resonance imaging showed incomplete myelination, but no evidence of lissencephaly. Cytogenetic analysis of the proband's peripheral blood showed an abnormal 17p. Fluorescence in situ hybridisation (FISH) with a Miller-Dieker cosmid probe did not detect a deletion for that area. Further analysis with a 17p telomere specific probe identified an unbalanced telomeric translocation. The same probe was used to determine the presence of an apparent balanced translocation t(9;17)(q34.3;p13.3) in the mother of the proband. The balanced translocation was confirmed with two cosmids that map distally on 9q34.3. Two phenotypically normal half sibs, a maternal aunt, a maternal uncle, and the maternal grandmother were found to be balanced translocation carriers as well. A subtle translocation carriers as well. A subtle translocation is one mechanism that can produce an abnormal phenotype in a patient who had a normal karyotype at lower band resolution levels.

A 7-year-old boy with 49,XXYYY karyotype is reported. Physical examination revealed facial dysmorphism, mild microcephaly, limitation of supination at the elbows, delayed bone age and moderate mental retardation.

Mutations in ASPM (abnormal spindle-like microcephaly associated) cause primary microcephaly in humans, a disorder characterized by a major reduction in brain size in the apparent absence of nonneurological anomalies. The function of the Aspm protein in neural progenitor cell expansion, as well as its localization to the mitotic spindle and midbody, suggest that it regulates brain development by a cell division-related mechanism. Furthermore, evidence that positive selection affected ASPM during primate evolution has led to suggestions that such a function changed during primate evolution. Here, we report that in Aspm mutant mice, truncated Aspm proteins similar to those causing microcephaly in humans fail to localize to the midbody during M-phase and cause mild microcephaly. A human ASPM transgene rescues this phenotype but, interestingly, does not cause a gain of function. Strikingly, truncated Aspm proteins also cause a massive loss of germ cells, resulting in a severe reduction in testis and ovary size accompanied by reduced fertility. These germline effects, too, are fully rescued by the human ASPM transgene, indicating that ASPM is functionally similar in mice and humans. Our findings broaden the spectrum of phenotypic effects of ASPM mutations and raise the possibility that positive selection of ASPM during primate evolution reflects its function in the germline.

We report on a 7 years and 4 months old Greek boy with mild microcephaly and dysmorphic facial features. He was a sociable child with maxillary hypoplasia, epicanthal folds, upslanting palpebral fissures with long eyelashes, and hypertelorism. His ears were prominent and dysmorphic, he had a long philtrum and a high arched palate. His weight was 17 kg (25th percentile) and his height 120 cm (50th percentile). High resolution chromosome analysis identified in 50% of the cells a normal male karyotype, and in 50% of the cells one chromosome 18 showed a terminal deletion from 18q21.32. Molecular cytogenetic investigation confirmed a del(18)(q21.32-qter) in the one chromosome 18, but furthermore revealed the presence of a duplication in q21.2 in the other chromosome 18. The case is discussed concerning comparable previously reported cases and the possible mechanisms of formation.

Very little is known about the molecular basis of autosomal recessive MR (ARMR) because in developed countries, small family sizes preclude mapping and identification of the relevant gene defects. We therefore chose to investigate genetic causes of ARMR in large consanguineous Iranian families. This study reports on a family with six mentally retarded members. Array-based homozygosity mapping and high-resolution microarray-based comparative genomic hybridization (array CGH) revealed a deletion of approximately 150-200 kb, encompassing the promoter and the first six exons of the MCPH1 gene, one out of four genes that have been previously implicated in ARMR with microcephaly. Reexamination of affected individuals revealed a high proportion of prematurely condensed chromosomes, which is a hallmark of this condition, but in spite of the severity of the mutation, all patients showed only borderline to mild microcephaly. Therefore the phenotypic spectrum of MCPH1 mutations may be wider than previously assumed, with ARMR being the only consistent clinical finding.

Duplication of chromosome 19, partial or complete, has rarely been described. Trisomy of its short arm (19p) was briefly reported in abstract form by Byrne et al 1 in 1980 in a newborn patient with dysmorphism and intrauterine growth retardation and in 1992 by Salbert et al 2 in a dysmorphic newborn male. The delineation of these two patients was hampered by deletion of the terminal band of chromosome 13 in the first case and partial deletion of distal chromosome 3q in the second case. The infant presented here is the first and only child of non-consanguineous parents. The family history is unremarkable apart from epilepsy in the maternal grandmother. The pregnancy was uneventful with no intrauterine growth retardation. The mother and the father were aged 28 and 35 years at the time of birth. He was born at 41 weeks of gestation by spontaneous delivery. He sat alone at 6 months, walked at 17 months, and …

A family comprising mother, father, and five children is described. Four of the children were found to excrete massive amounts of D(+)-glyceric acid in their urine. This was verified by gas chromatography-mass spectrometry and the configuration determined by capillary gas chromatography of O-acetylated menthyl esters. The excretion ranged from 10.8 to 19.9 mmol/24 h. The remaining child and the parents showed no evidence of this unusual metabolite. The virtual absence of clinical manifestations in this family was particularly interesting. Only two of the children showed any clinical abnormality and this was limited to mild microcephaly and speech delay; the other two children found to excrete large amounts of D(+)-glycerate were healthy and developmentally normal at 7 y and 9 y of age. There was a marked increase in the excretion rate of D(+)-glycerate in response to both oral fructose and serine loading. These results are consistent with a deficiency of D(+)-glycerate kinase and indicate the potentially benign nature of this disorder.

Two cases with association of Hirschsprung disease and preaxial polydactyly occurring in siblings were reported. The proband was a female infant examined on the 12th day after birth. Major findings were as follows: growth retardation, mild microcephaly, rightanophthalmia, left exophthalmus associated with double disk and coloboma choroidae, ocular hypotelorism, cleft lip and palate, and bilateral preaxial polydactyly. CT scan of the brain revealed agenesis of the corpus callosum and atrophy of the cerebral cortex. Autopsy revealed alobar holoprosencephaly and agenesis of the corpus callosum, right optic nerve and olfactory nerve. Aganglionosis of the rectumwas noted at a site 10 cm from the anus. When her brother was born, bilateral preaxial polydactyly was found. He had Hirschsprung disease as well.

Trigonocephaly was found in six relatives through three generations of one family. The propositus was ascertained at birth because of omphalocele. In addition to trigonocephaly, he had minor ear, vertebral, and genital abnormalities. His father had mild microcephaly, and both had minor eye abnormalities. None of the other four affected individuals had any other malformations. In this family, trigonocephaly is an autosomal dominant trait. The ratio of affected males to affected females was 5 to 1, and although the paucity of affected females is not statistically significant, we speculate that it may reflect variable expressivity or sex limitation of the trait. We conclude that the condition in this family represents a unique syndrome in which trigonocephaly is not associated with functional brain abnormalities and where craniosynostosis is limited to the metopic region.

IN our human gene localization studies we have sought abnormal inheritance patterns of qualitative gene markers and have evaluated possible gene dose effects through quantitative enzyme assays in patients with abnormal chromosome constitutions. During these studies a patient with the cat cry syndrome was found to have a half normal value for red blood cell triosephosphate isomerase (EC 5.3.1.1). Clinical features which suggest that the patient has the cat cry syndrome include mental and physical retardation, a weak plaintive cry, moon facies, mild microcephaly, epicanthal folds, antimongoloid slant to the palpebral fissures and hypertelorism1.