Expanding CEP290 mutational spectrum in ciliopathies

Ciliopathies are an expanding group of rare conditions characterized by multiorgan involvement, that are caused by mutations in genes encoding for proteins of the primary cilium or its apparatus. Among these genes, CEP290 bears an intriguing allelic spectrum, being commonly mutated in Joubert syndrome and related disorders (JSRD), Meckel syndrome (MKS), Senior-Loken syndrome and isolated Leber congenital amaurosis (LCA). Although these conditions are recessively inherited, in a subset of patients only one CEP290 mutation could be detected. To assess whether genomic rearrangements involving the CEP290 gene could represent a possible mutational mechanism in these cases, exon dosage analysis on genomic DNA was performed in two groups of CEP290 heterozygous patients, including five JSRD/MKS cases and four LCA, respectively. In one JSRD patient, we identified a large heterozygous deletion encompassing CEP290 C-terminus that resulted in marked reduction of mRNA expression. No copy number alterations were identified in the remaining probands. The present work expands the CEP290 genotypic spectrum to include multiexon deletions. Although this mechanism does not appear to be frequent, screening for genomic rearrangements should be considered in patients in whom a single CEP290 mutated allele was identified.

Cri du chat mosaicism: an unusual case of partial deletion and partial deletion/ duplication of the short arm of chromosome 5, leading to an unusual cri du chat phenotype

The Cri du Chat Syndrome (CdCS) is one of the most common deletion syndromes, involving the short arm of chromosome 5, with an incidence of 1 in 50.000 live births. The following are the characteristic features of this syndrome: microcephaly, hypertelorism, round face, micrognatia, epicanthic folds, prominent nasal bridge, hypotonia and severe psychomotor retardation. Patients also show a high pitched cry similar to the mewing of a cat. Deletions and duplications of chromosome 5p have been described in the literature. Mosaicism represents only 3% of this cytogenetic aberration. Up to date, only cases of de novo 5p mosaic anomalies involving two or three rearranged cell lines, with deletions and duplications, have been described. Herein, we report the first case of a patient affected by multiple congenital anomalies and a mosaicism, with two rearranged cell lines: one with a 5p deletion; the other with a 5p deletion/duplication. Our patient did not show the characteristic features described in patients with 5p duplications, but a phenotype compatible with the CdCS. Our case represents the first description of a mosaicism with deletion and deletion/duplication of a portion of the short arm of chromosome 5.

Duplication of the terminal band of the long arm of chromosome 7: a new case

We report on a new case of de novo duplication of the terminal band of chromosome 7, 46, XX dup(7) (q36 > qter), defined by fluorescence in situ hybridization (FISH), which cause a recognizable phenotype consisting of macrocephaly, prominent frontal bossing, slight developmental delay.

Partial proximal trisomy 10q syndrome: a new case

We report a case of partial proximal trisomy of the long arm of chromosome 10 confirmed by fluorescence in situ hibridization (FISH) performed with whole chromosome 10 specific painting and specific yac clones. The phenotypic findings, compared to those found in other published cases with the same karyotype, support the recognition of a distinctive partial proximal trisomy 10q syndrome (10q11-->q22).

Cerebellar vermis defect, oligophrenia, congenital ataxia, and hepatic fibrocirrhosis without coloboma and renal abnormalities: report of three cases

We describe 3 children (2 siblings aged 10 and 3 years, and 1 sporadic case aged 13 years) with cerebellar vermis defect associated with oligophrenia, congenital ataxia, and hepatic fibrocirrhosis. Differently from what is reported in COACH syndrome, coloboma and renal involvement were absent. Since in one patient hepatic involvement was subclinical and early therapy seemed to prevent disease progression, the presence of liver disease should be carefully investigated in any patient with ataxia and midline cerebellar defects.

Elevation of serum creatine kinase as the only manifestation of an intragenic deletion of the dystrophin gene in three unrelated families

This study reports three children from three unrelated families, aged from 9 to 12 years, who were investigated because of the incidental finding of elevated serum creatine kinase (CK) levels and were found to have a dystrophinopathy. The molecular defect consisted of a deletion of variable extent within the central rod domain of the dystrophin gene, involving either exons 32-44 or 48-51 or 48-53. In each family we found the same deletion in at least one adult male relative aged from 40 to 77 years, who was either completely asymptomatic or had very mild muscle involvement (thin muscles and/or mild scoliosis), with normal or borderline CK levels. This study suggests once again that deletions of the central rod domain of dystrophin may be associated with elevation of serum CK as the only manifestation and that prediction of the clinical severity based solely on the molecular findings should be interpreted with caution.

Activation of the metabotropic glutamate receptor is neuroprotective during nitric oxide toxicity in primary hippocampal neurons of rats

Metabotropic glutamate receptors (mGluRs) can influence neuronal survival and have been shown to be neuroprotective during glutamate toxicity in retinal cells and in cortical neurons. The mechanisms that mediate protection by this group of receptors are not clear. Since nitric oxide (NO) production can lead to neuronal cell death during excessive glutamate release, we examined whether neuronal survival was directly linked to mGluR activity and the NO pathway. Treatment with the mGluR4 receptor subtype agonist, L-(+)-2-amino-4-phosphonobutyric acid, in hippocampal cell cultures protected neurons during NO exposure. Treatment with L-(+)-2-amino-3-phosphonopropionic acid, an antagonist of the mGluR1 receptor subtype and inhibitor of inositol trisphosphate formation, did not significantly alter neuronal survival during NO administration. We conclude that activation of the mGluR4 receptor protects hippocampal neurons from NO toxicity and that the mechanism of NO induced neurodegeneration does not appear to involve inhibition of the mGluR1 receptor subtype activity or the phosphoinositide system.

Neuroprotection by peptide growth factors against anoxia and nitric oxide toxicity requires modulation of protein kinase C

Basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF) are neuroprotective during anoxia and nitric oxide (NO) toxicity. Signal transduction systems that modulate protein kinase C (PKC) also can modulate the toxic effects of anoxia and NO. We therefore examined whether PKC was involved in the protective effects of bFGF and EGF during anoxia and NO toxicity. Down-regulation or inhibition of PKC activity before anoxia or NO exposure prevented hippocampal neuronal degeneration. Yet, this protective effect of inhibition of PKC activity was not present with the coadministration of growth factors. Combined inhibition of PKC activity and application of bFGF or EGF lessened the protective mechanisms of the growth factors. In addition, the protective ability of the growth factors was lost during anoxia and NO exposure with the activation of PKC, suggesting that at least a minimal degree of PKC activation is necessary for growth factor protection. Although modulation of PKC activity may be a necessary prerequisite for protection against anoxia and NO toxicity by bFGF and EGF, only inhibition of PKC activity, rather than application of the growth factors, was protective following exposure to NO. These results suggest that the mechanism of protection by bFGF and EGF during anoxia and NO toxicity appears initially to be dependent on a minimum degree of PKC activation, but that other signal transduction pathways independent of PKC also may mediate protection by peptide growth factors.

Blepharophimosis, ptosis, epicanthus inversus syndrome, a new case associated with de novo balanced autosomal translocation [46,XY,t(3;7)(q23;q32)]

This paper reports a further case of blepharophimosis, ptosis, epicanthus inversus (BPES) syndrome associated with a reciprocal translocation [46,XY,t(3;7)(q23;q32)], involving band 3q23. This case supports the assignment of a BPES gene(s) to the 3q23 region.

Hypothalamic growth hormone deficiency in a patient with ring chromosome 18

We report on a boy with a ring 18 chromosome associated with hypothalamic growth hormone (GH) deficiency. A 12-month trial of GH replacement therapy (0.5 U/kg/week) resulted in a marked growth acceleration. Our findings emphasise the need of evaluating GH secretion in patients with abnormalities of the 18 chromosome.

Nitric oxide: a downstream mediator of calcium toxicity in the ischemic cascade

Loss of cellular calcium homeostasis or the production of nitric oxide (NO) have been cited as possible mechanisms that may contribute to neuronal degeneration during ischemia. We therefore examined whether cellular calcium blockade, using the agent HA1077, was protective during anoxia in hippocampal neuronal cell cultures, and whether the in vitro effects of this drug were linked to the NO pathway. Administration of the agent during anoxia was neuroprotective in neuronal cell culture. In contrast, HA1077 did not protect hippocampal neurons during NO exposure. In addition, inhibition of NO synthesis in conjunction with HA1077 application during anoxia did not significantly increase survival beyond the maximum protection afforded by HA1077 alone. These results suggest that calcium may be an initial messenger in the ischemic cascade, but that subsequent neuronal degeneration is dependent upon the NO pathway.