Low Detection Rates of Genetic FH in Cohort of Patients With Severe Hypercholesterolemia in the United Arabic Emirates

Background: Programs to screen for Familial hypercholesterolemia (FH) are conducted worldwide. In Western societies, these programs have been shown to be cost-effective with hit/detection rates of 1 in 217–250. Thus far, there is no published data on genetic FH in the Gulf region. Using United Arab Emirates as a proxy for the Gulf region, we assessed the prevalence of genetically confirmed FH in the Emirati population sample. Materials and Methods: We recruited 229 patients with LDL-C >95(th) percentile and employed a customized next generation sequencing pipeline to screen canonical FH genes (LDLR, APOB, PCSK9, LDLRAP1). Results: Participants were characterized by mean total cholesterol and low-density lipoprotein cholesterol (LDL-c) of 6.3 ± 1.1 and 4.7 ± 1.1 mmol/L respectively. Ninety-six percent of the participants were using lipid-lowering medication with mean corrected LDL-c values of 10.0 ± 3.0 mmol/L 15 out of 229 participants were found to suffer from genetically confirmed FH. Carriers of causal genetic variants for FH had higher on-treatment LDL-c compared to those without causal variants (5.7 ± 1.5 vs 4.7 ± 1.0; p = 3.7E-04). The groups did not differ regarding high-density lipoprotein cholesterol, triglycerides, body mass index, blood pressure, glucose, and glycated haemoglobin. Conclusion: This study reveals a low 7% prevalence of genetic FH in Emiratis with marked hypercholesterolemia as determined by correcting LDL-c for the use of lipid-lowering treatment. The portfolio of mutations identified is, to a large extent, unique and includes gene duplications. Our findings warrant further studies into origins of hypercholesterolemia in these patients. This is further supported by the fact that these patients are also characterized by high prevalence of type 2 diabetes (42% in the current study cohort) which already puts them at an increased risk of atherosclerotic cardiovascular disease. These results may also be useful in public health initiatives for FH cascade screening programs in the UAE and maybe the Gulf region

Copy Number Variation in Patients with Disorders of Sex Development Due to 46,XY Gonadal Dysgenesis

Disorders of sex development (DSD), ranging in severity from mild genital abnormalities to complete sex reversal, represent a major concern for patients and their families. DSD are often due to disruption of the genetic programs that regulate gonad development. Although some genes have been identified in these developmental pathways, the causative mutations have not been identified in more than 50% 46,XY DSD cases. We used the Affymetrix Genome-Wide Human SNP Array 6.0 to analyse copy number variation in 23 individuals with unexplained 46,XY DSD due to gonadal dysgenesis (GD). Here we describe three discrete changes in copy number that are the likely cause of the GD. Firstly, we identified a large duplication on the X chromosome that included DAX1 (NR0B1). Secondly, we identified a rearrangement that appears to affect a novel gonad-specific regulatory region in a known testis gene, SOX9. Surprisingly this patient lacked any signs of campomelic dysplasia, suggesting that the deletion affected expression of SOX9 only in the gonad. Functional analysis of potential SRY binding sites within this deleted region identified five putative enhancers, suggesting that sequences additional to the known SRY-binding TES enhancer influence human testis-specific SOX9 expression. Thirdly, we identified a small deletion immediately downstream of GATA4, supporting a role for GATA4 in gonad development in humans. These CNV analyses give new insights into the pathways involved in human gonad development and dysfunction, and suggest that rearrangements of non-coding sequences disturbing gene regulation may account for significant proportion of DSD cases

The rhox homeobox gene family shows sexually dimorphic and dynamic expression during mouse embryonic gonad development

Reproductive capacity is fundamental to the survival of all species. Consequently, much research has been undertaken to better understand gametogenesis and the interplay between germ cells and the somatic cell lineages of the gonads

FAM20A mutations can cause enamel-renal syndrome (ERS).

Enamel-renal syndrome (ERS) is an autosomal recessive disorder characterized by severe enamel hypoplasia, failed tooth eruption, intrapulpal calcifications, enlarged gingiva, and nephrocalcinosis. Recently, mutations in FAM20A were reported to cause amelogenesis imperfecta and gingival fibromatosis syndrome (AIGFS), which closely resembles ERS except for the renal calcifications. We characterized three families with AIGFS and identified, in each case, recessive FAM20A mutations: family 1 (c.992G>A; g.63853G>A; p.Gly331Asp), family 2 (c.720-2A>G; g.62232A>G; p.Gln241_Arg271del), and family 3 (c.406C>T; g.50213C>T; p.Arg136* and c.1432C>T; g.68284C>T; p.Arg478*). Significantly, a kidney ultrasound of the family 2 proband revealed nephrocalcinosis, revising the diagnosis from AIGFS to ERS. By characterizing teeth extracted from the family 3 proband, we demonstrated that FAM20A(-/-) molars lacked true enamel, showed extensive crown and root resorption, hypercementosis, and partial replacement of resorbed mineral with bone or coalesced mineral spheres. Supported by the observation of severe ectopic calcifications in the kidneys of Fam20a null mice, we conclude that FAM20A, which has a kinase homology domain and localizes to the Golgi, is a putative Golgi kinase that plays a significant role in the regulation of biomineralization processes, and that mutations in FAM20A cause both AIGFS and ERS

Backscatter Scanning Electron Micrographs (bSEMs) of molar (#18) crown.

<p><i>A:</i> The bSEM of molar after it was cut sagitally (mesial-distally). <i>B:</i> Higher magnification of region boxed in A showing regions magnified in C–F. The bowtie-shaped structure in the lower right is the calcified pulp chamber. Most of the coronal dentin has been resorbed, with some of it replaced by well-formed lamellar bone (b). <i>C–E:</i> Region showing dense, rough, crusty mineral in place of enamel (e) covering sclerotic dentin (d) that is fused to lamellar bone (b). There appears to be sites of active resorption of the dentin and bone (arrowheads). <i>F:</i> The pulp calcification (pc) is comprised of coalesced spheres that resemble the crusty “enamel” in mineral density embedded in a second, less mineralized material like dentin or acellular cementum that lacks osteocyte lacunae.</p

Scanning Electron Micrographs (SEMs) of mineral covering coronal dentin in a molar (#18) split for SEM examination.

<p><i>Left:</i> Enamel layer in normal molar <i>Right:</i> Mineral covering dentin in <i>FAM20</i>^−/− molar. No long thin crystals with rod/interrod organization are observed in the <i>FAM20</i>^−/− molar.</p

Backscatter Scanning Electron Micrographs (bSEMs) of molar (#18) roots.

<p><i>A:</i> The bSEM of molar after it was cut sagitally (mesial-distally). <i>B:</i> Higher magnification of smaller box in A showing the layered build-up resembling cellular cementum. Arrowheads mark the dentin-cementum border. <i>C–D:</i> Higher magnifications of the larger box in A showing the thick layers of “cellular cementum” covering the roots. In panel D a dark line is placed at the dentin surface. <i>E:</i> Higher magnification of the larger box in panel C showing the thick layers of “cellular cementum” covering the roots and how the lamellar pattern suggests that deposition of these layers was punctuated by periods of resorption that sometimes penetrated into the dentin. <i>F–G:</i> Higher magnification of the smaller box in panel C also showing how deposition of the layers of acellular cementum was punctuated by resorption that sometimes penetrated into the dentin.</p

Family 1 from the Caribbean with <i>FAM20A</i> mutation c.992G>A; g.63853G>A; p.G331D.

<p><i>A:</i> Pedigree. A dot marks person who donated samples for DNA sequencing. <i>B: FAM20A</i> exon 7 DNA sequencing chromatograms. The proband's parents (II:1 and II:2) were both heterozygous (R = A or G) at cDNA position 992 (arrowheads). The proband (III-1) had the c.992G>A transition mutation in both alleles of <i>FAM20A</i>. This mutation changed a conserved glycine with an aspartic acid (p.G331D). The proband's affected younger sister (III-4) and her infant niece (IV:1) were also homozygous for this mutation (not shown). II:1 and III:8 were heterozygous for a recognized polymorphism (rs2302234) in exon 7 (K = A or C) unrelated to the phenotype. <i>C:</i> Proband's panoramic radiograph. Note the many unerupted teeth. The mandibular and maxillary unerupted second molars show concave occlusal surfaces without enamel (arrowheads). <i>D:</i> Proband's oral photos. The maxillary central incisors are restored. The clinical crowns were short with hypoplastic enamel. There was a deep anterior overbite, a posterior cross-bite, and retained mandibular primary molars (letters K, L, S, T).</p

Backscatter Scanning Electron Micrographs (bSEMs) of molar (#32).

<p><i>A:</i> The bSEM of molar after it was cut sagitally (mesial-distally). <i>B:</i> Rough “enamel” (e) covering sclerotic dentin. <i>C:</i> Acellular cementum covering sclerotic root dentin. <i>D–E:</i> Highly mineralized pulp or radicular calcifications (pc) comprised of coalesced spheres above the root furcation and associated with a less mineralized material that contacts dentin (d). <i>F:</i> The radicular area appears to be comprised entirely of acellular cementum (ac) or lamellar bone from the furcation to the highly mineralized coalesced spheres. <i>G:</i> Root dentin covered with a thick layer of acellular cementum (ac) or bone. A thin line of more highly mineralized material, possibly cementum (c), separates these layers. <i>H:</i> The material covering root dentin is deposited in layers and sometimes fills in areas of localized root resorption.</p