Pathogenic SCN2A variants cause early-stage dysfunction in patient-derived neurons

Pathogenic heterozygous variants in SCN2A, which encodes the neuronal sodium channel NaV1.2, cause different types of epilepsy or intellectual disability (ID)/autism without seizures. Previous studies using mouse models or heterologous systems suggest that NaV1.2 channel gain-of-function typically causes epilepsy, whereas loss-of-function leads to ID/autism. How altered channel biophysics translate into patient neurons remains unknown. Here, we investigated iPSC-derived early-stage cortical neurons from ID patients harboring diverse pathogenic SCN2A variants [p.(Leu611Valfs*35); p.(Arg937Cys); p.(Trp1716*)] and compared them with neurons from an epileptic encephalopathy (EE) patient [p.(Glu1803Gly)] and controls. ID neurons consistently expressed lower NaV1.2 protein levels. In neurons with the frameshift variant, NaV1.2 mRNA and protein levels were reduced by ~ 50%, suggesting nonsense-mediated decay and haploinsufficiency. In other ID neurons, only protein levels were reduced implying NaV1.2 instability. Electrophysiological analysis revealed decreased sodium current density and impaired action potential (AP) firing in ID neurons, consistent with reduced NaV1.2 levels. In contrast, epilepsy neurons displayed no change in NaV1.2 levels or sodium current density, but impaired sodium channel inactivation. Single-cell transcriptomics identified dysregulation of distinct molecular pathways including inhibition of oxidative phosphorylation in neurons with SCN2A haploinsufficiency and activation of calcium signaling and neurotransmission in epilepsy neurons. Together, our patient iPSC-derived neurons reveal characteristic sodium channel dysfunction consistent with biophysical changes previously observed in heterologous systems. Additionally, our model links the channel dysfunction in ID to reduced NaV1.2 levels and uncovers impaired AP firing in early-stage neurons. The altered molecular pathways may reflect a homeostatic response to NaV1.2 dysfunction and can guide further investigations.

New syndrome of mental retardation, Robin sequence, and brachydactyly

We report on two sibs, brother and sister, affected with a multiple congenital anomalies/mental retardation (MCA/MR) syndrome, characterized by mild to moderate psychomotor delay, Robin sequence, peculiar facial appearance, and brachydactyly. To our knowledge, this combination of anomalies has not been reported previously. The occurrence of a similar pattern of anomalies in brother and sister suggests autosomal recessive inheritance; however, dominant transmission with reduced penetrance cannot be ruled out in our patients, since minor clinical signs, such as brachydactyly, are also present in the father.

Two novel mutations confirm FGD1 is responsible for the Aarskog syndrome

The Aarskog syndrome or facio-genital dysplasia (FGDY, MIM No. 305400) is an X-linked condition characterized by short stature, macrocephaly, facial, genital and skeletal anomalies. It is caused by mutation of the FGD1 gene mapped to the Xp11.21 region. To date, only one point mutation has been reported in an affected family, consisting of the insertion of an additional guanine residue at nucleotide 2122 of exon 7, which causes premature translational termination. We now report the finding of two novel FGD1 mutations, a missense mutation in a family of Italian origin and a deletion of 3 exons in a sporadic case from Germany. These mutations confirm the role of FGD1 as the gene responsible for the Aarskog syndrome.

Nonsyndromal overgrowth in males with mild psychomotor delay

Over the last 3 years we ascertained 42 patients for statural overgrowth and/or macrocephaly, who also had mild developmental delay. There were 39 males and three females, two of whom were sisters. In no case was tall stature a familial characteristic. Family history was unremarkable, except for the case of the two sisters. Physical examination did not demonstrate any consistent pattern of malformations or anomalies identifying a syndrome, known or unknown. Chromosomes were apparently normal and the molecular test for the fragile X syndrome yielded normal results in all cases. Muscular hypotonia, advanced bone age, and epilepsy were relatively consistent manifestations. The hypothalamus-pituitary axis seemed to be intact when tested through the blood levels of insulin-like growth factors I and II and of the insulin-like growth binding protein 3, and the excess of growth was apparently growth hormone independent. The condition comprising excessive growth, developmental delay, muscular hypotonia, absence of a consistent pattern of physical anomalies, and apparently sporadic occurrence, largely limited to males, may be heterogenous.

Correlation between Goldmann perimetry and maximal electroretinogram response in retinitis pigmentosa

To evaluate the relationship between Goldmann perimetry and maximal electroretinographic responses in patients with retinitis pigmentosa, analyses were performed on 220 affected subjects and separately on two subgroups with autosomal dominant (n = 35) and autosomal recessive (n = 29) inheritance. Electroretinograms were recorded averaging 100 iterations elicited with a 20-lux/s, 0.5-Hz white flash ganzfeld stimulation. The peripheral isopters of the visual fields were delimited with I4e, IIIe and V4e targets, measured on conventional perimetry charts with a light pen and expressed in square centimeters. Unlike most previously published reports, this investigation showed a definite correlation (p = 0.0001) between maximal electroretinographic response amplitude and visual field areas. This correlation was more evident for I4e and IIIe isopters (r = 0.89 and 0.87, respectively) than for V4e isopter (r = 0.69). This phenomenon appears to be related to distortion occurring on standard isometric charts and to spatial summation effects in the peripheral field. Such correlations held for both the autosomal dominant and autosomal recessive subgroups. It appears that, if enough accuracy is provided, maximal electroretinographic responses and Goldmann visual fields are both good measures of the remaining functioning retina in nonsyndromic retinitis pigmentosa, irrespective of inheritance models and dystrophic patterns.

Clinical heterogeneity of dominant optic atrophy: the contribution of visual function investigations to diagnosis

BACKGROUND

The variability of the visual function impairment in dominant optic atrophy (DOA) makes it difficult to diagnose the disease within genealogies. Physiologic investigations were conducted on a family with DOA to evaluate methods of detecting clinical and subclinical signs in obligate heterozygotes, in order to identify affected subjects within the genealogy and to formulate the individual and reproductive risks.

METHODS

Investigations included tests for color vision, contrast sensitivity function (CSF), kinetic and static computerized perimetry, transient pattern reversal visual evoked potentials (VEPs) and steady-state flash VEPs.

RESULTS

Eight subjects from the pedigree were diagnosed as having DOA. Two of them were unaware of their affection, and six showed wide clinical variability. CSF paralleled the central visual impairment, but was also slightly impaired in the two unaware subjects. Static computerized perimetry disclosed mild sensitivity defects in the central visual fields in these two patients. VEPs showed heterogeneous results as well, ranging from normal findings to severely altered tracings.

CONCLUSIONS

This investigation suggests that combined clinical and functional evaluation is necessary to diagnose DOA. Particularly, the combined use of computerized perimetry, CSF, and VEPs allowed the identification of cases at a subclinical stage.

Autosomal dominant simple microphthalmos

Congenital bilateral microphthalmos is a rare malformation of the eye, which ranges from extreme to mild reduction of total axial length. Microphthalmos may occur as an isolated ocular abnormality or as part of a systemic disorder, and different classifications of the condition have been attempted. We describe a large pedigree with 14 persons in four generations affected with bilateral microphthalmos without other ocular or systemic signs. An autosomal dominant trait with complete penetrance is proposed. Five subjects underwent a complete ophthalmological evaluation. The total axial length was measured by A scan ultrasonography in all persons. Ultrasonography showed a reduction of the total axial length (range 18.4-19.7 mm) and a reduced vitreous cavity length (range 11.4-13.5 mm) in all investigated patients. All the patients had microcornea (range 8-9.7 mm). No other ocular anomalies or associated systemic malformations were found. A review of published reports also suggests that simple, partial, posterior, pure microphthalmos and nanophthalmos are similar clinical entities sharing total axial length and vitreous cavity length reduction. Therefore, the term simple microphthalmos is proposed to identify these clinical conditions.

Karyotype modifications in human malignant melanoma cell cultures after treatment with azelaic acid

Azelaic acid (AzAc) is a C9 dicarboxylic acid which has recently been shown to have some therapeutic applications in skin diseases of different aetiologies. In order to study the in vitro activity of AzAc five human malignant melanoma primary cell cultures were treated for up to 60 days with 10 mM C9 2Na; the growth characteristics were defined by growth curve and the cytogenetics by Giemsa standard technique and GTG banding technique. Our data demonstrated an inhibition in replication of all five melanomas and the disappearance of the clones with chromosomal markers in four out of five melanomas after AzAc treatment.

Lentigo maligna. Cytogenetic, ultrastructural, and phenotypic characterization of a primary cell culture

Lentigo maligna is an early cutaneous neoplastic lesion. This article presents the cytogenetic, ultrastructural, and phenotypic characterization of a primary cell culture obtained from a patient affected with lentigo maligna. Two cellular clones were identified, both characterized by chromosomal markers involving chromosome 10 with a breakpoint at 10q26.