NID1 variant associated with occipital cephaloceles in a family expressing a spectrum of phenotypes

Autosomal dominant Dandy‐Walker malformation and occipital cephalocele (ADDWOC) is a rare, congenital, and incompletely penetrant malformation that is considered to be part of the Dandy‐Walker spectrum of disorders. Affected individuals often present with an occipital cephalocele with a bony skull defect, but typically have normal neurological development. Here, we report on a three‐generation family in which individuals have variable phenotypes that are consistent with the ADDWOC spectrum: arachnoid cysts in the proband and his maternal grandfather, an occipital cephalocele in the proband and his brother, and a small bony defect in the proband's mother. Whole exome sequencing identified a rare heterozygous variant in NID1 (NM_002508.2:c.1162C>T, (p.Gln388Ter)) in the proband, his brother, and his mother. Sanger sequencing confirmed the presence of this variant in the maternal grandfather. The identical c.1162C>T variant was previously identified in variably affected members of a three‐generation family with ADDWOC. This case report provides further evidence that variants in NID1 may be clinically relevant for the development of a phenotype that is consistent with ADDWOC, and extends the phenotype of NID1‐associated ADDWOC to include arachnoid cysts. Given that the Dandy‐Walker malformation itself is not a pre‐requisite to this spectrum of phenotypes, we also suggest a novel term for the NID1‐associated disorder in order to give emphasis to this phenotypic variability: “Autosomal Dominant Posterior Fossa Anomalies with Occipital Cephaloceles.”     

A novel HYLS1 homozygous mutation in living siblings with Joubert syndrome

The p.Asp211Gly homozygous HYLS1 mutation is so far known to cause only hydrolethalus syndrome, a lethal malformation syndrome. We report living sibling patients with a homozygous no‐stop mutation in exon 4 of HYLS1, NM_145014.2:c.900A>C (p.Ter300TyrextTer11) in the second decade of life. The proband has Joubert syndrome (JS). The younger brother also has JS and an enlarged posterior fossa that was initially diagnosed as Dandy–Walker malformation. The present mutation is unique as it affects the stop codon. The product protein HYLS1 plays an essential role in the formation of the primary cilium. This report provides insight into the spectrum of disorders involving midline brain defects closely related to cilium dysfunction or ciliopathy.     

NID1-related autosomal dominant Dandy-Walker malformation with occipital cephalocele in three generations

The combination of Dandy-Walker malformation and occipital cephalocele is a rare autosomal dominant condition, known as ADDWOC, and caused by mutations in NID1 or LAMC1.We present a three-generation family with variable manifestations of Dandy-Walker malformation and occipital cephalocele. They all have normal psychomotor development and lack neurological manifestations. Mutation analysis revealed a likely pathogenic missense variant in NID1 (c.3336T > G, p.Asn1112Lys), affecting an amino acid residue crucial in the nidogen/laminin interaction.     

Occurrence of Dandy‐Walker anomaly in a familial case of distal arthogryposis type IIB

We present a family affected with distal arthrogryposis type IIB (DA IIB) in three generations. The coincidental finding of Dandy‐Walker anomaly in the proposita arouses the question whether Dandy‐Walker anomaly is part of the DA IIB spectrum or whether the Aase‐Smith syndrome belongs to the DA spectrum. Am. J. Med. Genet. 95:477–481, 2000. © 2000 Wiley‐Liss, Inc.     

Novel association of Dandy–Walker malformation with CAPN15 variants expands the phenotype of oculogastrointestinal neurodevelopmental syndrome

Oculogastrointestinal neurodevelopmental syndrome has been described in seven previously published individuals who harbor biallelic pathogenic variants in the CAPN15 gene. Biallelic missense variants have been reported to demonstrate a phenotype of eye abnormalities and developmental delay, while biallelic loss of function variants exhibit phenotypes including microcephaly and craniofacial abnormalities, cardiac and genitourinary malformations, and abnormal neurologic activity. We report six individuals from three unrelated families harboring biallelic deleterious variants in CAPN15 with phenotypes overlapping those previously described for this disorder. Of the individuals affected, four demonstrate radiographic evidence of the classical triad of Dandy–Walker malformation including hypoplastic vermis, fourth ventricle enlargement, and torcular elevation. Cerebellar anomalies have not been previously reported in association with CAPN15-related disease. Here, we present three unrelated families with findings consistent with oculogastrointestinal neurodevelopmental syndrome and cerebellar pathology including Dandy–Walker malformation. To corroborate these novel clinical findings, we present supporting data from the mouse model suggesting an important role for this protein in normal cerebellar development. Our findings add six molecularly confirmed cases to the literature and additionally establish a new association of Dandy–Walker malformation with biallelic CAPN15 variants, thereby expanding the neurologic spectrum among patients affected by CAPN15-related disease.     

A recurrent germline BAP1 mutation and extension of the BAP1 tumor predisposition spectrum to include basal cell carcinoma

We report four previously undescribed families with germline BRCA1‐associated protein‐1 gene (BAP1) mutations and expand the clinical phenotype of this tumor syndrome. The tumor spectrum in these families is predominantly uveal malignant melanoma (UMM), cutaneous malignant melanoma (CMM) and mesothelioma, as previously reported for germline BAP1 mutations. However, mutation carriers from three new families, and one previously reported family, developed basal cell carcinoma (BCC), thus suggesting inclusion of BCC in the phenotypic spectrum of the BAP1 tumor syndrome. This notion is supported by the finding of loss of BAP1 protein expression by immunochemistry in two BCCs from individuals with germline BAP1 mutations and no loss of BAP1 staining in 53 of sporadic BCCs consistent with somatic mutations and loss of heterozygosity of the gene in the BCCs occurring in mutation carriers. Lastly, we identify the first reported recurrent mutation in BAP1 (p.R60X), which occurred in three families from two different continents. In two of the families, the mutation was inherited from a common founder but it arose independently in the third family.     

Homozygous nonsense mutation in SCHIP1/IQCJ‐SCHIP1 causes a neurodevelopmental brain malformation syndrome

We report a consanguineous Arab family with 3 affected siblings who display a disorder of global developmental delay, learning difficulties, facial dysmorphism, hearing impairments, and cataract. The clinical phenotype was associated with characteristic brain magnetic resonance imaging (MRI) features of axonal guidance defects involving anterior commissure agenesis as well as scattered areas of polymicrogyria‐cobblestone complex. Whole genome sequencing revealed a novel nonsense mutation (159609921C>T) that segregated in the family consistent in an autosomal recessive pattern. This mutation located in the C‐terminal region shared by the Schwanomin‐Interacting Protein1 (SCHIP1) isoforms including the IQCJ‐SCHIP1. The in vitro expression of SCHIP1 and IQCJ‐SCHIP1 truncated mutant isoforms (NM_001197109.1; p.R209* and NM_001197114.1; p.R501*, respectively) were markedly reduced as compared to their full‐length versions suggesting protein stability/folding impairment. The pathogenic nature of this mutation is supported by a previously reported mouse knockout of Schip1 isoforms, which phenocopied the human axon guidance abnormality. This is the first report of a SCHIP1/IQCJ‐SCHIP1 point mutation in humans associated with a neurological‐developmental phenotype.     

NF1 Molecular Characterization and Neurofibromatosis Type I Genotype–Phenotype Correlation: The French Experience

Neurofibromatosis type 1 (NF1) affects about one in 3,500 people in all ethnic groups. Most NF1 patients have private loss‐of‐function mutations scattered along the NF1 gene. Here, we present an original NF1 investigation strategy and report a comprehensive mutation analysis of 565 unrelated patients from the NF‐France Network. A NF1 mutation was identified in 546 of the 565 patients, giving a mutation detection rate of 97%. The combined cDNA/DNA approach showed that a significant proportion of NF1 missense mutations (30%) were deleterious by affecting pre‐mRNA splicing. Multiplex ligation‐dependent probe amplification allowed the identification of restricted rearrangements that would have been missed if only sequencing or microsatellite analysis had been performed. In four unrelated families, we identified two distinct NF1 mutations within the same family. This fortuitous association points out the need to perform an exhaustive NF1 screening in the case of molecular discordant‐related patients. A genotype–phenotype study was performed in patients harboring a truncating (N = 368), in‐frame splicing (N = 36), or missense (N = 35) mutation. The association analysis of these mutation types with 12 common NF1 clinical features confirmed a weak contribution of the allelic heterogeneity of the NF1 mutation to the NF1 variable expressivity.     

Laminin-1 (LM-111) in preeclampsia and systemic lupus erythematosus

Background: Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the production of antibodies. SLE has been associated with placental pathology, a finding that is also the determinant in preeclampsia (PE). Genetic evidence and serologic reports suggest laminin-1 (LM-111) as an immunogenic molecule and its polymorphic gene as a candidate gene for both disorders. Objective: To evaluate the association between LAMA1 (rs543355) and LAMC1 (rs20563) polymorphisms and the presence of SLE and PE as well as to determine serum levels of anti-LM-111 autoantibodies in the PE group. Methods: Group A: 169 women with PE and 172 healthy pregnant women. Group B: 204 women with SLE and 204 healthy women. Anti-LM-111 for group A was measured by ELISA and the genotyping was done by using a PCR system. Results: Group A: Levels of anti-LM-111 was similar in women with PE and the control group (p = 0.3). The allelic frequencies and genotypes did not show statistically significant differences for LAMA1 and LAMC1 polymorphisms. Group B: Significant differences between SLE patients and controls for rs543355 polymorphism were not observed. Nevertheless, LAMC1 rs20563 A-allele provided protection against the development of SLE (OR 0.73, 95%CI 0.55-0.96). Conclusions: Serum levels of anti-LM-111 at the third trimester of gestation do not seem to have any direct relationship with the presence of PE, and the SNPs evaluated are not associated with the risk of developing this disorder. LAMC1 polymorphism could be a protective factor for SLE.     

Recurrent agnathia–otocephaly caused by DNA replication slippage in PRRX1

Agnathia–otocephaly is a rare craniofacial malformation complex that is caused by de novo heterozygous and biallelic mutations in PRRX1 in two unrelated babies, respectively. We studied the PRRX1 gene in a non‐consanguineous Indonesian female infant who was diagnosed prenatally with severe retrognathia (bilateral Pruzansky type III). Her older affected brother died shortly after birth and had agnathia–otocephaly. A c.266_269dupAAAA frameshift mutation in the poly A tract in PRRX1 was identified in the proband while her father only had an inframe duplication (c.267_269dupAAA) of the adenosine trinucleotide residue. Expression of both mutations in COS7 cells showed loss of function of the frame shift mutation only. Results of SNP genotyping coupled with recurrence of this novel mutation in this family are consistent with a paternally derived germline mosaicism rather than autosomal recessive inheritance as predicted by the family history. Severe retrognathia (bilateral Pruzansky III) and agnathia–otocephaly represent a spectrum of craniofacial malformations in this family. © 2013 Wiley Periodicals, Inc.     

Cenani–Lenz syndrome and other related syndactyly disorders due to variants in LRP4, GREM1/FMN1, and APC: Insight into the pathogenesis and the relationship to polyposis through the WNT and BMP antagonistic pathways

Cenani–Lenz (C–L) syndrome is characterized by oligosyndactyly, metacarpal synostosis, phalangeal disorganization, and other variable facial and systemic features. Most cases are caused by homozygous and compound heterozygous missense and splice mutations of the LRP4 gene. Currently, the syndrome carries one OMIM number (212780). However, C–L syndrome‐like phenotypes as well as other syndactyly disorders with or without metacarpal synostosis/phalangeal disorganization are also known to be associated with specific LRP4 mutations, adenomatous polyposis coli (APC) truncating mutations, genomic rearrangements of the GREM1‐FMN1 locus, as well as FMN1 mutations. Surprisingly, patients with C–L syndrome‐like phenotype caused by APC truncating mutations have no polyposis despite the increased levels of β catenin. The LRP4 and APC proteins act on the WNT (wingless‐type integration site family) canonical pathway, whereas the GREM‐1 and FMN1 proteins act on the bone morphogenetic protein (BMP) pathway. In this review, we discuss the different mutations associated with C–L syndrome, classify its clinical features, review familial adenomatous polyposis caused by truncating APC mutations and compare these mutations to the splicing APC mutation associated with syndactyly, and finally, explore the pathophysiology through a review of the cross talks between the WNT canonical and the BMP antagonistic pathways.     

Spectrum and detection rate of L1CAM mutations in isolated and familial cases with clinically suspected L1‐disease

Mutations in L1CAM, the gene encoding the L1 neuronal cell adhesion molecule, lead to an X‐linked trait characterized by one or more of the symptoms of hydrocephalus, adducted thumbs, agenesis or hypoplasia of corpus callosum, spastic paraplegia, and mental retardation (L1‐disease). We screened 153 cases with prenatally or clinically suspected X‐chromosomal hydrocephalus for L1CAM mutations by SSCP analysis of the 28 coding exons and regulatory elements in the 5′‐untranslated region of the gene. Forty‐six pathogenic mutations were found (30.1% detection rate), the majority consisting of nonsense, frameshift, and splice site mutations. In eight cases, segregation analysis disclosed recent de novo mutations. Statistical analysis of the data indicates a significant effect on mutation detection rate of (i) family history, (ii) number of L1‐disease typical clinical findings, and (iii) presence or absence of signs not typically associated with L1CAM‐disease. Whereas mutation detection rate was 74.2% for patients with at least two additional cases in the family, only 16 mutations were found in the 102 cases with negative family history (15.7% detection rate). Our data suggest a higher than previously assumed contribution of L1CAM mutations in the pathogenesis of the heterogeneous group of congenital hydrocephalus. Am. J. Med. Genet. 92:40–46, 2000. © 2000 Wiley‐Liss, Inc.     

A homozygous FKRP start codon mutation is associated with Walker–Warburg syndrome,the severe end of the clinical spectrum

van Reeuwijk J, Olderode‐Berends MJW, van den Elzen C, Brouwer OF, Roscioli T, van Pampus MG, Scheffer H, Brunner HG, van Bokhoven H, Hol FA. A homozygous FKRP start codon mutation is associated with Walker–Warburg syndrome, the severe end of the clinical spectrum. Dystroglycanopathies are a heterogeneous group of disorders caused by defects in the glycosylation pathway of α‐dystroglycan. The clinical spectrum ranges from severe congenital muscular dystrophy with structural brain and eye involvement to a relatively mild adult onset limb‐girdle muscular dystrophy without brain abnormalities and normal intelligence. Mutations have been identified in one of six putative or demonstrated glycosyltransferases. Many different FKRP mutations have been identified, which cover the complete clinical spectrum of dystroglycanopathies. In contrast to the other known genes involved in these disorders, genotype–phenotype correlations are not obvious for FKRP mutations. To date, no homozygous or compound heterozygous null mutations have been identified in FKRP, suggesting that null mutations in FKRP could result in embryonic lethality. We report a family with two siblings carrying a homozygous mutation in the start codon of FKRP that is likely to result in a loss of functional FKRP protein. The clinical phenotype of the patients was consistent with Walker–Warburg syndrome, the most severe disorder in the disease spectrum of dystroglycanopathies.     

3D structural analysis of protein O‐mannosyl kinase,POMK, a causative gene product of dystroglycanopathy

Orchestration of the multiple enzymes engaged in O‐mannose glycan synthesis provides a matriglycan on α‐dystroglycan (α‐DG) which attracts extracellular matrix (ECM) proteins such as laminin. Aberrant O‐mannosylation of α‐DG leads to severe congenital muscular dystrophies due to detachment of ECM proteins from the basal membrane. Phosphorylation at C6‐position of O‐mannose catalyzed by protein O‐mannosyl kinase (POMK) is a crucial step in the biosynthetic pathway of O‐mannose glycan. Several mis‐sense mutations of the POMK catalytic domain are known to cause a severe congenital muscular dystrophy, Walker–Warburg syndrome. Due to the low sequence similarity with other typical kinases, structure–activity relationships of this enzyme remain unclear. Here, we report the crystal structures of the POMK catalytic domain in the absence and presence of an ATP analogue and O‐mannosylated glycopeptide. The POMK catalytic domain shows a typical protein kinase fold consisting of N‐ and C‐lobes. Mannose residue binds to POMK mainly via the hydroxyl group at C2‐position, differentiating from other monosaccharide residues. Intriguingly, the two amino acid residues K92 and D228, interacting with the triphosphate group of ATP, are donated from atypical positions in the primary structure. Mutations in this protein causing muscular dystrophies can now be rationalized.     

Mutation in the SYNJ1 Gene Associated with Autosomal Recessive,Early‐Onset Parkinsonism

Autosomal recessive, early‐onset Parkinsonism is clinically and genetically heterogeneous. Here, we report the identification, by homozygosity mapping and exome sequencing, of a SYNJ1 homozygous mutation (p.Arg258Gln) segregating with disease in an Italian consanguineous family with Parkinsonism, dystonia, and cognitive deterioration. Response to levodopa was poor, and limited by side effects. Neuroimaging revealed brain atrophy, nigrostriatal dopaminergic defects, and cerebral hypometabolism. SYNJ1 encodes synaptojanin 1, a phosphoinositide phosphatase protein with essential roles in the postendocytic recycling of synaptic vesicles. The mutation is absent in variation databases and in ethnically matched controls, is damaging according to all prediction programs, and replaces an amino acid that is extremely conserved in the synaptojanin 1 homologues and in SAC1‐like domains of other proteins. Sequencing the SYNJ1 ORF in unrelated patients revealed another heterozygous mutation (p.Ser1422Arg), predicted as damaging, in a patient who also carries a heterozygous PINK1 truncating mutation. The SYNJ1 gene is a compelling candidate for Parkinsonism; mutations in the functionally linked protein auxilin cause a similar early‐onset phenotype, and other findings implicate endosomal dysfunctions in the pathogenesis. Our data delineate a novel form of human Mendelian Parkinsonism, and provide further evidence for abnormal synaptic vesicle recycling as a central theme in the pathogenesis.     

Identification and functional analysis of an ADAMTSL1 variant associated with a complex phenotype including congenital glaucoma,craniofacial, and other systemic features in a three‐generation human pedigree

Developmental glaucoma can occur as an isolated or syndromic condition and is genetically heterogeneous. We describe a three‐generation family affected with developmental glaucoma, myopia, and/or retinal defects associated with variable craniofacial/dental, auditory, brain, renal, and limb anomalies. Whole‐exome sequencing identified a heterozygous c.124T> C, p.(Trp42Arg) allele in ADAMTSL1; cosegregation analysis confirmed the presence of this allele in four affected family members. The mutation affects a highly conserved residue and is strongly predicted to have a deleterious effect on protein function. Trp42 is normally modified by protein C‐mannosylation, an unusual post‐translational modification. Comparison of ADAMTSL1‐WT (also known as punctin‐1) and ADAMTSL1‐p.Trp42Arg in vitro demonstrated that the latter was not secreted from transfected cells but retained intracellularly. Moreover, ADAMTSL1‐p.Trp42Arg reduced secretion of cotransfected wild‐type ADAMTSL1, suggesting a dominant negative effect for this mutation. These data imply a multisystem role for ADAMTSL1 and present the first disease‐associated variant affecting a C‐mannosylation motif.     

Airway remodelling and inflammation in asthma are dependent on the extracellular matrix protein fibulin‐1c

Asthma is a chronic inflammatory disease of the airways. It is characterized by allergic airway inflammation, airway remodelling, and airway hyperresponsiveness (AHR). Asthma patients, in particular those with chronic or severe asthma, have airway remodelling that is associated with the accumulation of extracellular matrix (ECM) proteins, such as collagens. Fibulin‐1 (Fbln1) is an important ECM protein that stabilizes collagen and other ECM proteins. The level of Fbln1c, one of the four Fbln1 variants, which predominates in both humans and mice, is increased in the serum and airways fluids in asthma but its function is unclear. We show that the level of Fbln1c was increased in the lungs of mice with house dust mite (HDM)‐induced chronic allergic airway disease (AAD). Genetic deletion of Fbln1c and therapeutic inhibition of Fbln1c in mice with chronic AAD reduced airway collagen deposition, and protected against AHR. Fbln1c‐deficient (Fbln1c^–/–) mice had reduced mucin (MUC) 5 AC levels, but not MUC5B levels, in the airways as compared with wild‐type (WT) mice. Fbln1c interacted with fibronectin and periostin that was linked to collagen deposition around the small airways. Fbln1c^–/– mice with AAD also had reduced numbers of α‐smooth muscle actin‐positive cells around the airways and reduced airway contractility as compared with WT mice. After HDM challenge, these mice also had fewer airway inflammatory cells, reduced interleukin (IL)‐5, IL‐13, IL‐33, tumour necrosis factor (TNF) and CXCL1 levels in the lungs, and reduced IL‐5, IL‐33 and TNF levels in lung‐draining lymph nodes. Therapeutic targeting of Fbln1c reduced the numbers of GATA3‐positive Th2 cells in the lymph nodes and lungs after chronic HDM challenge. Treatment also reduced the secretion of IL‐5 and IL‐13 from co‐cultured dendritic cells and T cells restimulated with HDM extract. Human epithelial cells cultured with Fbln1c peptide produced more CXCL1 mRNA than medium‐treated controls. Our data show that Fbln1c may be a therapeutic target in chronic asthma. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.