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Abstract Background The breadth of the clinical spectrum underlying Pelizaeus-Merzbacher disease and spastic paraplegia type 2 is due to the extensive allelic heterogeneity in the X-linked PLP1 gene encoding myelin proteolipid protein (PLP). PLP1 mutations range from gene duplications of variable size found in 60-70% of patients to intragenic lesions present in 15-20% of patients. Methods Forty-eight male patients from 38 unrelated families with a PLP1-related disorder were studied. All DNA samples were screened for PLP1 gene duplications using real-time PCR. PLP1 gene sequencing analysis was performed on patients negative for the duplication. The mutational status of all 14 potential carrier mothers of the familial PLP1 gene mutation was determined as well as 15/24 potential carrier mothers of the PLP1 duplication. Results and Conclusions PLP1 gene duplications were identified in 24 of the unrelated patients whereas a variety of intragenic PLP1 mutations were found in the remaining 14 patients. Of the 14 different intragenic lesions, 11 were novel; these included one nonsense and 7 missense mutations, a 657-bp deletion, a microdeletion and a microduplication. The functional significance of the novel PLP1 missense mutations, all occurring at evolutionarily conserved residues, was analysed by the MutPred tool whereas their potential effect on splicing was ascertained using the Skippy algorithm and a neural network. Although MutPred predicted that all 7 novel missense mutations would be likely to be deleterious, in silico analysis indicated that four of them (p.Leu146Val, p.Leu159Pro, p.Thr230Ile, p.Ala247Asp) might cause exon skipping by altering exonic splicing elements. These predictions were then investigated in vitro for both p.Leu146Val and p.Thr230Ile by means of RNA or minigene studies and were subsequently confirmed in the case of p.Leu146Val. Peripheral neuropathy was noted in four patients harbouring intragenic mutations that altered RNA processing, but was absent from all PLP1-duplication patients. Unprecedentedly, family studies revealed the de novo occurrence of the PLP1 duplication at a frequency of 20%.

Abstract Background Eukaryotic translation initiation factor 2B (eIF2B), a guanine nucleotide exchange factor (GEF) and a key regulator of translation initiation under normal and stress conditions, causes an autosomal recessive leukodystrophy of a wide clinical spectrum. EBV-immortalised lymphocytes (EIL) from eIF2B-mutated patients exhibit a decrease in eIF2B GEF activity. eIF2B-mutated primary fibroblasts have a hyper-induction of activating transcription factor 4 (ATF4) which is involved in the protective unfolded protein response (UPR), also known as the ER-stress response. We tested the hypothesis that EIL from eIF2B-mutated patients also exhibit a heightened ER-stress response. Methods We used thapsigargin as an ER-stress agent and looked at polysomal profiles, rate of protein synthesis, translational activation of ATF4, and transcriptional induction of stress-specific mRNAs (ATF4, CHOP, ASNS, GRP78) in normal and eIF2B-mutated EIL. We also compared the level of stress-specific mRNAs between EIL and primary lymphocytes (PL). Results Despite the low eIF2B GEF activity in the 12 eIF2B-mutated EIL cell lines tested (range 40-70% of normal), these cell lines did not differ from normal EIL in their ATF4-mediated ER-stress response. The absence of hyper-induction of ATF4-mediated ER-stress response in eIF2B-mutated EIL in contrast to primary fibroblasts is not related to their transformation by EBV. Indeed, PL exhibited a higher induction of the stress-specific mRNAs in comparison to EIL, but no hyper-induction of the UPR was noticed in the eIF2B-mutated cell lines in comparison to controls. Conclusions Taken together with work of others, our results demonstrate the absence of a major difference in ER-stress response between controls and eIF2B-mutated cells. Therefore, components of the ER-stress response cannot be used as discriminantory markers in eIF2B-related disorders.

Abstract Background Premature Ovarian Failure (POF), defined as the development of hypergonadotropic amenorrhea before the age of 40 years, occurs in about 1% of all women. Other than karyotype abnormalities, very few genes are known to be associated with this ovarian dysfunction. Recently, in seven patients who presented with POF and white matter abnormalities on MRI (ovarioleukodystrophy) eight mutationswere found in EIF2B2, 4 and 5. Methods To further test the involvement of known mutations of EIF2B genes in POF, we screened 93 patients with POF who did not have identified leukodystrophy or neurological symptoms. We evaluated these eight mutations and two additional mutations that had been found in patients with milder forms of eIF2B-related disorders. We used restriction enzymes and direct sequencing. Results None of the known mutations in EIF2B genes, either homozygous or heterozygous, were identified in our 93 patients with pure 46,XX POF. The upper 95 % confidence limit of the proportion 0/93 is 3.2%. Conclusions We conclude that eIF2B mutations, already described in cases of POF associated with white matter abnormalities, are an uncommon cause of pure spontaneous premature ovarian failure.

X linked subcortical laminar heterotopia and lissencephaly syndrome (XSCLH/ LIS) is an intriguing disorder of cortical development, which causes classical lissencephaly with severe mental retardation and epilepsy in hemizygous males, and subcortical laminar heterotopia (SCLH) associated with milder mental retardation and epilepsy in heterozygous females. Here we report an exclusion mapping study carried out in three unrelated previously described families in which males are affected with lissencephaly and females with SCLH, using 38 microsatellite markers evenly distributed on the X chromosome. Most of the X chromosome was excluded and potential intervals of assignment in Xq22.3-q23 or in Xq27 are reported. Although the number of informative meioses did not allow a decision between these two loci, it is worth noting that the former interval is compatible with the mapping of a breakpoint involved in a de novo X;autosomal balanced translocation 46,XX,t(X;2)(q22;p25) previously described in a female with classical lissencephaly. In addition, haplotype inheritance in two families showed a grandpaternal origin of the mutation and suggested in one family the presence of mosaicism in germline cells of normal transmitting males. [ABSTRACT FROM PUBLISHER]