Novel NALCN biallelic truncating mutations in siblings with IHPRF1 syndrome.

Infantile hypotonia with psychomotor retardation and characteristic facies-1 (IHPRF1) is a severe autosomal recessive neurologic disorder with onset at birth or in early infancy. It is caused by mutations in the NALCN gene that encodes a voltage-independent, cation channel permeable to NM, K+ and Ca2+ and forms a channel complex with UNCSO and UNC79. So far, only 4 homozygous mutations have been found in 11 cases belonging to 4 independent consanguineous families. We studied a Sardinian family with 2 siblings presenting dysmorphic facies, hypotonia, psychomotor retardation, epilepsy, absent speech, sleep disturbance, hyperkinetic movement disorder, cachexia and chronic constipation. Polymorphic generalized seizures started at 4 and 6 years, respectively. Anti-epileptic drugs (AEDs) therapy was efficient for female proband's epilepsy, but the male still has weekly seizures. Whole exome sequencing identified 2 novel truncating mutations in NALCN allowing to assess the clinical phenotype to IHPRF1. This is the fifth family reported worldwide, and these are the first European cases with IHPRF1 syndrome with biallelic truncating mutations of NALCN.

Crisponi syndrome: a new mutation in CRLF1 gene associated with moderate outcome.

SUMMARY: Crisponi syndrome (CS) is a rare, autosomal recessive disorder, characterized by hyperthermia, extensive muscular contractions in the face after even minimal stimuli or crying, hypertonia, opisthotonus, camptodactyly, and typical facial features. Recently, it has been demonstrated that CRLF1 (cytokine receptor-like factor 1) gene mutation is associated with CS. Here we report a case of CS with a new mutation in the CRLF1 gene associated with moderate clinical phenotype.

The putative forkhead transcription factor FOXL2 is mutated in blepharophimosis/ptosis/epicanthus inversus syndrome.

In type I blepharophimosis/ptosis/epicanthus inversus syndrome (BPES), eyelid abnormalities are associated with ovarian failure. Type II BPES shows only the eyelid defects, but both types map to chromosome 3q23. We have positionally cloned a novel, putative winged helix/forkhead transcription factor gene, FOXL2, that is mutated to produce truncated proteins in type I families and larger proteins in type II. Consistent with an involvement in those tissues, FOXL2 is selectively expressed in the mesenchyme of developing mouse eyelids and in adult ovarian follicles; in adult humans, it appears predominantly in the ovary. FOXL2 represents a candidate gene for the polled/intersex syndrome XX sex-reversal goat.

Jagged-1 mutation analysis in Italian Alagille syndrome patients.

Alagille syndrome (AGS) is an autosomal dominant disorder with developmental abnormalities affecting the liver, heart, eyes, vertebrae, and craniofacial region. The Jagged-1 (JAG1) gene, which encodes a ligand of Notch, has recently been found mutated in AGS. In this study, mutation analysis of the JAG1 gene performed on 20 Italian AGS patients led to the identification of 15 different JAG1 mutations, including a large deletion of the 20p12 region, six frameshift, three nonsense, three splice-site, and two missense mutations. The two novel missense mutations were clustered in the 5' region, while the remaining mutations were scattered throughout the gene. The spectrum of mutations in Italian patients was similar to that previously reported. We also studied in detail a complex splice site mutation, 3332dupl8bp, which was shown to lead to an abnormal JAG1 mRNA, resulting in a premature stop codon. With the exception of the missense mutations, the majority of the JAG1 mutations are therefore likely to produce truncated proteins. Since the phenotype of the patient with a complete deletion of the JAG1 gene is indistinguishable from that of patients with intragenic mutations, our study further supports the hypothesis that haploinsufficiency is the most common mechanism involved in AGS pathogenesis. Furthermore, our data confirmed the absence of a correlation between the genotype of the JAG1 gene and the AGS phenotype.

Glypican 3 and glypican 4 are juxtaposed in Xq26.1.

Recently, we have shown that mutations in the X-linked glypican 3 (GPC3) gene cause the Simpson-Golabi-Behmel overgrowth syndrome (SGBS; ). The next centromeric gene detected is another glypican, glypican 4 (GPC4), with its 5' end 120763bp downstream of the 3' terminus of GPC3. One recovered GPC4 cDNA with an open reading frame of 1668nt encodes a putative protein containing three heparan sulfate glycosylation signals and the 14 signature cysteines of the glypican family. This protein is 94.3% identical to mouse GPC4 and 26% identical to human GPC3. In contrast to GPC3, which produces a single transcript of 2.3kb and is stringently restricted in expression to predominantly mesoderm-derived tissues, Northern analyses show that GPC4 produces two transcripts, 3.4 and 4.6kb, which are very widely expressed (though at a much higher level in fetal lung and kidney). Interestingly, of 20 SGBS patients who showed deletions in GPC3, one was also deleted for part of GPC4. Thus, GPC4 is not required for human viability, even in the absence of GPC3. This patient shows a complex phenotype, including the unusual feature of hydrocephalus; but because an uncle with SGBS is less affected, it remains unclear whether the GPC4 deletion itself contributes to the phenotype.

Analysis of exon/intron structure and 400 kb of genomic sequence surrounding the 5'-promoter and 3'-terminal ends of the human glypican 3 (GPC3) gene.

GPC3, the gene modified in the Simpson-Golabi-Behmel gigantism/overgrowth syndrome (SGBS), is shown to span more than 500 kb of genomic sequence, with the transcript beginning 197 bp 5' of the translational start site. The Xq26.1 region containing GPC3 as the only known gene has been extended to > 900 kb by sequence analysis of flanking BAC clones. Two GC isochores (40.6 and 42.6% GC) are observed at the 5' and 3' ends of the locus, with a large repertoire of repetitive sequences that includes an unusual cluster of four L1 elements > 92% identical over 2.8 kb. Eight exons, accounting for the full 2.4-kb GPC3 cDNA, have been sequenced along with neighboring intronic regions. PCR assays have been developed to amplify each exon and exon/intron junction sequence, to help discriminate instances of SGBS among individuals with overgrowth syndromes and to facilitate mutational analysis of lesions in the gene.