Cholesteryl ester storage disease (CESD) is caused by deficient lysosomal acid lipase (LAL) activity, predominantly resulting in cholesteryl ester (CE) accumulation, particularly in the liver, spleen, and macrophages throughout the body. The disease is characterized by microvesicular steatosis leading to liver failure, accelerated atherosclerosis and premature demise. Although CESD is rare, it is likely that many patients are unrecognized or misdiagnosed. Here, the findings in 135 CESD patients described in the literature are reviewed. Diagnoses were based on liver biopsies, LAL deficiency and/or LAL gene (LIPA) mutations. Hepatomegaly was present in 99.3% of patients; 74% also had splenomegaly. When reported, most patients had elevated serum total cholesterol, LDL-cholesterol, triglycerides, and transaminases (AST, ALT, or both), while HDL-cholesterol was decreased. All 112 liver biopsied patients had the characteristic pathology, which is progressive, and includes microvesicular steatosis, which leads to fibrosis, micronodular cirrhosis, and ultimately to liver failure. Pathognomonic birefringent CE crystals or their remnant clefts were observed in hepatic cells. Extrahepatic manifestations included portal hypertension, esophageal varices, and accelerated atherosclerosis. Liver failure in 17 reported patients resulted in liver transplantation and/or death. Genotyping identified 31 LIPA mutations in 55 patients; 61% of mutations were the common exon 8 splice-junction mutation (E8SJM(-1G>A)), for which 18 patients were homozygous. Genotype/phenotype correlations were limited; however, E8SJM(-1G>A) homozygotes typically had early-onset, slowly progressive disease. Supportive treatment included cholestyramine, statins, and, ultimately, liver transplantation. Recombinant LAL replacement was shown to be effective in animal models, and recently, a phase I/II clinical trial demonstrated its safety and indicated its potential metabolic efficacy.

Allan-Herndon-Dudley syndrome was among the first of the X-linked mental retardation syndromes to be described (in 1944) and among the first to be regionally mapped on the X chromosome (in 1990). Six large families with the syndrome have been identified, and linkage studies have placed the gene locus in Xq13.2. Mutations in the monocarboxylate transporter 8 gene (MCT8) have been found in each of the six families. One essential function of the protein encoded by this gene appears to be the transport of triiodothyronine into neurons. Abnormal transporter function is reflected in elevated free triiodothyronine and lowered free thyroxine levels in the blood. Infancy and childhood in the Allan-Herndon-Dudley syndrome are marked by hypotonia, weakness, reduced muscle mass, and delay of developmental milestones. Facial manifestations are not distinctive, but the face tends to be elongated with bifrontal narrowing, and the ears are often simply formed or cupped. Some patients have myopathic facies. Generalized weakness is manifested by excessive drooling, forward positioning of the head and neck, failure to ambulate independently, or ataxia in those who do ambulate. Speech is dysarthric or absent altogether. Hypotonia gives way in adult life to spasticity. The hands exhibit dystonic and athetoid posturing and fisting. Cognitive development is severely impaired. No major malformations occur, intrauterine growth is not impaired, and head circumference and genital development are usually normal. Behavior tends to be passive, with little evidence of aggressive or disruptive behavior. Although clinical signs of thyroid dysfunction are usually absent in affected males, the disturbances in blood levels of thyroid hormones suggest the possibility of systematic detection through screening of high-risk populations.

The filamins are cytoplasmic proteins that regulate the structure and activity of the cytoskeleton by cross-linking actin into three-dimensional networks, linking the cell membrane to the cytoskeleton and serving as scaffolds on which intracellular signaling and protein trafficking pathways are organized (reviewed in refs. 1,2). We identified mutations in the gene encoding filamin B in four human skeletal disorders. We found homozygosity or compound heterozygosity with respect to stop-codon mutations in autosomal recessive spondylocarpotarsal syndrome (SCT, OMIM 272460) and missense mutations in individuals with autosomal dominant Larsen syndrome (OMIM 150250) and the perinatal lethal atelosteogenesis I and III phenotypes (AOI, OMIM 108720; AOIII, OMIM 108721). We found that filamin B is expressed in human growth plate chondrocytes and in the developing vertebral bodies in the mouse. These data indicate an unexpected role in vertebral segmentation, joint formation and endochondral ossification for this ubiquitously expressed cytoskeletal protein.Morphogenesis in vertebrate organisms requires the integration of extracellular signals with alterations in the cellular cytoskeleton. Filamins regulate the organization of cytoskeletal F-actin into either parallel bundles or orthogonal gel networks 3 and also mediate interactions between subcortical actin networks and transmembrane receptors to modulate cell-cell, cell-matrix and intracytoplasmic signal transduction 1,2,4 . Mammals have three filamin genes, FLNA, FLNB and FLNC. FLNA and FLNB seem to be ubiquitously expressed 5,6 ; FLNC is predominantly expressed in muscle. Human filamin genes are highly similar with conserved exon-intron structure, and there is ∼70% homology at the protein level 2,7 . The filamin monomer comprises an N-terminal actin binding domain (ABD) followed by a series of 24 β-sheet repeats that collectively bind many cytoplasmic and transmembrane proteins 1,2 . Filamins exist in vivo as dimers. Dimerization, leading to homo-and possibly heterodimer formation, is mediated by interactions between C-terminal sequences 5,8,9 . Mutations in FLNA produce a spectrum of X-linked malformation and osteochondrodysplasia syndromes. FLNA loss-of-function mutations are usually embryonically lethal in males and underlie a neuronal migration disorder in females 10 . Mutations producing structural changes in the protein lead to numerous developmental anomalies in the brain, skeleton and viscera 11 .Recently the gene associated with SCT, an autosomal recessive disorder characterized by short stature and vertebral, carpal and tarsal fusions 12,13 , was localized on chromosome 3p14 (ref. 14). These studies and further recombination mapping (data not shown) identified a 4.7-cM candidate region, which included a 1.4-Mb region of homozygosity containing 14 genes. Mutations were not found in the candidate genes WNT5A 14 , ASB14 and IL17RD (also known as SEF) in affected individuals from the linked families. The gene FLNB localizes to this interval and, considering the r...

Neurofibromatosis type 1 (NF1) is one of the most frequent genetic disorders, affecting 1:3,000 worldwide. Identification of genotype–phenotype correlations is challenging because of the wide range clinical variability, the progressive nature of the disorder, and extreme diversity of the mutational spectrum. We report 136 individuals with a distinct phenotype carrying one of five different NF1 missense mutations affecting p.Arg1809. Patients presented with multiple café‐au‐lait macules (CALM) with or without freckling and Lisch nodules, but no externally visible plexiform neurofibromas or clear cutaneous neurofibromas were found. About 25% of the individuals had Noonan‐like features. Pulmonic stenosis and short stature were significantly more prevalent compared with classic cohorts (P < 0.0001). Developmental delays and/or learning disabilities were reported in over 50% of patients. Melanocytes cultured from a CALM in a segmental NF1‐patient showed two different somatic NF1 mutations, p.Arg1809Cys and a multi‐exon deletion, providing genetic evidence that p.Arg1809Cys is a loss‐of‐function mutation in the melanocytes and causes a pigmentary phenotype. Constitutional missense mutations at p.Arg1809 affect 1.23% of unrelated NF1 probands in the UAB cohort, therefore this specific NF1 genotype–phenotype correlation will affect counseling and management of a significant number of patients.

All Mendelian hypertension syndromes described to date involve increased sodium reabsorption in the distal nephron. 5 The sole exception is autosomal-dominant hypertension with BDE (HTNB, OMIM #112410), first reported in a Turkish kindred. 2,6 HTNB was linked to chromosome 12p in six unrelated families. 2,7,8 The locus accounts for a ~50 mm Hg mean blood pressure difference at age 50 years. 2 The penetrance is 100% (Fig. 1a). Previously, we reported a rearrangement on chromosome 12p common to all families. 8,9 A linkage study in Chinese hypertensive families without BDE coincided with the HTNB locus, supporting relevance to essential hypertension. 10 Whole-genome sequencing of Turkish family members revealed a heterozygous missense mutation in PDE3A (Gene ID: 5139), a gene encoding a cGMP/cAMP phosphodiesterase with a prominent role in the heart, VSMC, oocytes and platelets. 11 Resequencing of all 48 affected persons in six unrelated families identified six independently clustered heterozygous missense mutations in exon 4 (Fig. 1a, b Supplementary Fig. 1).We detected none of the previously described chromosomal breakpoints on chromosome 12p12.2-12.1, perhaps due to high repetitive content in the breakpoint regions Fig. 2a-c). 4 A haplotype analysis identified a novel recombination that reduced the linkage interval and eliminated an inversion common to all affected individuals in the six families (Fig. 2c). 9 In contrast, the affected mother's haplotype showed co-segregation with the more severe brachydactyly phenotype.PDEs are involved during early stages of osteogenesis. 12 PDE4D mutations have been associated with severe brachydactyly in acrodysostosis. 13,14 In mice, Pde3a was expressed in the developing limbs, consistent with a role during chondrogenesis (Fig. 2d, Supplementary Fig. 3a, b). Chondrogenic downregulation of PTHLH encoding PTHrP was associated with BDE. 15 We also observed PTHLH downregulation in chondrogenically induced fibroblasts from affected persons (Fig. 2e, Supplementary Fig. 3c).We addressed the functional consequences of the identified PDE3A mutations in HeLa cells expressing the six mutations. Forskolin or L-arginine stimulated the adenylate or guanylate cyclases to enhance cellular cAMP or cGMP levels, respectively. 16,17 We detected significantly reduced cAMP levels, consistent with gain-of-function mutations with no change in cGMP levels for the PDE3A mutations ( Supplementary Fig. 4a, b). Three PDE3A isoforms, PDE3A1 (microsomal), PDE3A2 and PDE3A3 (microsomal and cytosolic), have been identified in human myocardium. 18,19 PDE3A3 does not contain the sequence harboring the detected mutations. The predominant isoform in VSMC is PDE3A2. 18,20 To directly elucidate the mutations' effects, we compared the Michaelis-Menten kinetics of cAMPhydrolytic activity for recombinant T445N FLAG-tagged PDE3A1 and PDE3A1-WT and the tagged A2 isoforms purified from transfected cells (Fig. 3a, b, Supplementary Fig. 4d-k). The T445N mutation increased the affinity of both enzyme's isoforms for cAM...

We have identified KIF11 mutations in individuals with syndromic autosomal-dominant microcephaly associated with lymphedema and/or chorioretinopathy. Initial whole-exome sequencing revealed heterozygous KIF11 mutations in three individuals with a combination of microcephaly and lymphedema from a microcephaly-lymphedema-chorioretinal-dysplasia cohort. Subsequent Sanger sequencing of KIF11 in a further 15 unrelated microcephalic probands with lymphedema and/or chorioretinopathy identified additional heterozygous mutations in 12 of them. KIF11 encodes EG5, a homotetramer kinesin motor. The variety of mutations we have found (two nonsense, two splice site, four missense, and six indels causing frameshifts) are all predicted to have an impact on protein function. EG5 has previously been shown to play a role in spindle assembly and function, and these findings highlight the critical role of proteins necessary for spindle formation in CNS development. Moreover, identification of KIF11 mutations in patients with chorioretinopathy and lymphedema suggests that EG5 is involved in the development and maintenance of retinal and lymphatic structures.

Whole-exome sequencing of 13 individuals with developmental delay commonly accompanied by abnormal muscle tone and seizures identified de novo missense mutations enriched within a sub-region of GNB1, a gene encoding the guanine nucleotide-binding protein subunit beta-1, Gβ. These 13 individuals were identified among a base of 5,855 individuals recruited for various undiagnosed genetic disorders. The probability of observing 13 or more de novo mutations by chance among 5,855 individuals is very low (p = 7.1 × 10(-21)), implicating GNB1 as a genome-wide-significant disease-associated gene. The majority of these 13 mutations affect known Gβ binding sites, which suggests that a likely disease mechanism is through the disruption of the protein interface required for Gα-Gβγ interaction (resulting in a constitutively active Gβγ) or through the disruption of residues relevant for interaction between Gβγ and certain downstream effectors (resulting in reduced interaction with the effectors). Strikingly, 8 of the 13 individuals recruited here for a neurodevelopmental disorder have a germline de novo GNB1 mutation that overlaps a set of five recurrent somatic tumor mutations for which recent functional studies demonstrated a gain-of-function effect due to constitutive activation of G protein downstream signaling cascades for some of the affected residues.

The constitutional t(11;22) translocation is the only known recurrent non-Robertsonian translocation in humans. Offspring are susceptible to der(22) syndrome, a severe congenital anomaly disorder caused by 3&rcolon;1 meiotic nondisjunction events. We previously localized the t(11;22) translocation breakpoint to a region on 22q11 within a low-copy repeat termed "LCR22" and within an AT-rich repeat on 11q23. The LCR22s are implicated in mediating different rearrangements on 22q11, leading to velocardiofacial syndrome/DiGeorge syndrome and cat-eye syndrome by homologous recombination mechanisms. The LCR22s contain AT-rich repetitive sequences, suggesting that such repeats may mediate the t(11;22) translocation. To determine the molecular basis of the translocation, we cloned and sequenced the t(11;22) breakpoint in the derivative 11 and 22 chromosomes in 13 unrelated carriers, including two de novo cases and der(22) syndrome offspring. We found that, in all cases examined, the reciprocal exchange occurred between similar AT-rich repeats on both chromosomes 11q23 and 22q11. To understand the mechanism, we examined the sequence of the breakpoint intervals in the derivative chromosomes and compared this with the deduced normal chromosomal sequence. A palindromic AT-rich sequence with a near-perfect hairpin could form, by intrastrand base-pairing, on the parental chromosomes. The sequence of the breakpoint junction in both derivatives indicates that the exchange events occurred at the center of symmetry of the palindromes, and this resulted in small, overlapping staggered deletions in this region among the different carriers. On the basis of previous studies performed in diverse organisms, we hypothesize that double-strand breaks may occur in the center of the palindrome, the tip of the putative hairpin, leading to illegitimate recombination events between similar AT-rich sequences on chromosomes 11 and 22, resulting in deletions and loss of the palindrome, which then could stabilize the DNA structure.