Generalized arterial calcification of infancy (GACI) is a rare autosomal-recessive disease characterized by extensive arterial calcification in infancy, with clinical manifestations such as arterial stenoses and heart failure. The ENPP1 inactivation mutation has been identified as a potential defect in most of the cases of GACI, while mutations in ABCC6 are demonstrated in patients who are genotyped as pseudoxanthoma elasticum and only limited cases of GACI are reported. Whole-exome sequencing was applied for the detection of pathogenic variants. Copy-number variants of pathogenic genes were also evaluated through a bioinformatic process and were further validated by real-time quantitative PCR. In this report, we described the clinical information and treatment of a patient with extensive arterial calcification. We have identified the underlying cause as biallelic mutations in ABCC6 (NM_00117: exon30, c.4223_4227dupAGCTC p.(Leu1410Serfs*56)) and a unique exonic deletion that spans from the first to the fourth exons of ABCC6 (chr16:16313388-16330869)). This discovery was made by utilizing a combined genetic testing approach. With the review of previously reported GACI patients with ABCC6 mutation, our work contributed to enriching the mutation spectrum of GACI and providing further information on this rare form of inherited disorder.

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Pseudoxanthoma elasticum, a heritable multisystem ectopic mineralization disorder, is caused by inactivating mutations in the ABCC6 gene. The encoded protein, ABCC6, a transmembrane transporter, has a specialized efflux function in hepatocytes by contributing to plasma levels of inorganic pyrophosphate, a potent inhibitor of mineralization in soft connective tissues. Reduced plasma inorganic pyrophosphate levels underlie the ectopic mineralization in pseudoxanthoma elasticum. In this study, we characterized the pathogenicity of three human ABCC6 missense variants using an adenovirus-mediated liver-specific ABCC6 transgene expression system in an Abcc6-/- mouse model of pseudoxanthoma elasticum. Variants p.L420V and p.R1064W were found benign because they had abundance and plasma membrane localization in hepatocytes similar to the wild-type human ABCC6 transgene, normalized plasma inorganic pyrophosphate levels, and prevented mineralization in the dermal sheath of vibrissae in muzzle skin, a phenotypic hallmark in the Abcc6-/- mice. In contrast, p.S400F was shown to be pathogenic because it failed to normalize plasma inorganic pyrophosphate levels and had no effect on ectopic mineralization despite its normal expression and proper localization in hepatocytes. These results showed that adenovirus-mediated hepatic ABCC6 expression in Abcc6-/- mice can provide a model system to effectively elucidate the multifaceted functional consequences of human ABCC6 missense variants identified in patients with pseudoxanthoma elasticum.

BACKGROUND: This article is a case report of pseudoxanthoma elasticum (PXE) which was diagnosed based on significant angioid streaks (AS) with choroidal neovascularization (CNV) and regain normal visual function by intravitreal injection with Conbercept.
METHODS: A 51-year-old woman was referred to the Ophthalmology Department of Qingdao Municipal Hospital (Qingdao, China) on September 14, 2020 for metamorphopsia and loss of vision in the left eye in the preceding three days. Past history: high myopia for more than 30 years, best corrected visual acuity (BCVA) of both eyes was 1.0 (5 m Standard Logarithm Visual Acuity chart in decimal notations), hypertension for six years, and cerebral infarction two years ago, no history of ocular trauma or surgeries or similar patients in family was documented. We used methods for observation, including fundus examination, optical coherence tomography (OCT), fluorescein angiography combined with indocyanine green angiography (FFA + ICGA). Due to her symptoms and manifestations, along with the appearance of her neck skin, which resembled \'chicken skin\', we speculated that she should be further examined at the Department of Dermatology by tissue paraffin section and molecular pathology analyses, and the diagnosis of PXE was then confirmed. After intravitreal injection with Conbercept (10 mg/ml, 0.2 ml, Chengdu Kanghong Biotechnologies Co., Ltd.; Chengdu, Sichuan, China) she regained her BCVA.
CONCLUSIONS: This patient regained her best corrected visual acuity through intravitreal injection with Conbercept. To the best of our knowledge, no publications are available on cases in which a vision loss and the normal visual function can be reverted by intravitreal injection with Conbercept. Although PXE is a disease with low incidence and thus no effective cure established, targeted symptomatic treatment can effectively retard the disease progression and improve visual function, such as intravitreal injection with Conbercept.

暂无摘要。

Pseudoxanthoma elasticum (PXE), the prototype of heritable ectopic mineralization disorders, manifests with deposition of calcium hydroxyapatite crystals in the skin, eyes and arterial blood vessels. This autosomal recessive disorder, due to mutations in ABCC6, is usually diagnosed around the second decade of life. In the spectrum of heritable ectopic mineralization disorders are also generalized arterial calcification of infancy (GACI), with extremely severe arterial calcification diagnosed by prenatal ultrasound or perinatally, and arterial calcification due to CD73 deficiency (ACDC) manifesting with arterial and juxta-articular mineralization in the elderly; the latter disorders are caused by mutations in ENPP1 and NT5E, respectively. The unifying pathomechanistic feature in these three conditions is reduced plasma levels of inorganic pyrophosphate (PPi), a powerful endogenous inhibitor of ectopic mineralization. Several on-going attempts to develop treatments for these conditions, either with the goal to normalize PPi plasma levels or by means of preventing calcium hydroxyapatite deposition independent of PPi, are in advanced preclinical levels or in early clinical trials. This overview summarizes the prospects of treatment development for ectopic mineralization disorders, with PXE, GACI and ACDC as the target diseases, from the 2020 vantage point.

In the past two decades, there has been great progress in identifying the molecular basis and pathomechanistic details in pseudoxanthoma elasticum (PXE), a heritable multisystem ectopic mineralization disorder. Although the identification of pathogenic variants in ABCC6 has been critical for understanding the disease process, genetic modifiers have been disclosed that explain the phenotypic heterogeneity of PXE. Adding to the genetic complexity of PXE are PXE-like phenotypes caused by pathogenic variants in other ectopic mineralization-associated genes. This review summarizes the current knowledge of the genetics and candidate modifier genes in PXE, a multifactorial disease at the genome-environment interface.

UNASSIGNED: Pseudoxanthoma elasticum (PXE) is a multisystem heritable disorder caused by mutations in the Abcc6 gene. The disease is characterized by ectopic mineralization of the skin, eyes, and arterial blood vessels. Previous studies have suggested that cardiovascular complications in patients with PXE are caused in part by premature atherosclerosis. The aim of this study is to determine the effect of an atherogenic diet on ectopic mineralization.
UNASSIGNED: We used Abcc6 tm1JfK mice (Abcc6 -/- mice) as an established preclinical model of PXE. The offspring at age of 4 weeks were divided into two groups and fed the standard control laboratory diet (control group) and the atherogenic diet. Serum lipid profiles and bile acids were measured, and steatosis and tissue mineralization were evaluated by histopathologic analysis and chemical calcium quantification assay, respectively.
UNASSIGNED: After 50-58 weeks of feeding an atherogenic diet, the concentrations of total cholesterol, low-density lipoprotein/very-low-density lipoprotein cholesterol, and bile acids were significantly higher in the Abcc6 -/- mice on the atherogenic diet (180.9 ± 14.8 g/L, 145.9 ± 12.9 g/L, and 9.7 ± 1.4 μmol/L, respectively) than in Abcc6 -/- mice on a control diet (85.2 ± 4.8 g/L, 25.1 ± 5.5 g/L, and 3.3 ± 0.5 μmol/L, respectively) (P < 0.001). Hypercholesterolemia was accompanied by extensive lipid accumulation in the liver and aorta, a characteristic feature of steatosis. The direct calcium assay demonstrated significantly increased mineralization of the muzzle skin containing the dermal sheath of vibrissae (57.2 ± 4.4 μmol Ca/gram tissue on the atherogenic diet and 43.9 ± 2.2 μmol Ca/gram tissue on control diet; P < 0.01), a reproducible biomarker of the ectopic mineralization process in these mice. An increased frequency of mineralization was also observed in the kidneys and eyes of mice on the atherogenic diet (P < 0.01).
UNASSIGNED: These observations suggest that the atherogenic diet caused hypercholesterolemia and accelerated ectopic mineralization in the Abcc6 -/- mice. Our findings have clinical implications for patients with PXE, a currently intractable disorder with considerable morbidity and occasional mortality.

Urinary calculi are characterized by high incidence and recurrence rate, which is a challenge in urology. The theory of Randall plaque is widely recognized by scholars. The mechanism of Randall plaque formation includes vascular calcification, osteogenic transformation and so on. However, it still lacks a unified theory for the Randall plaque formation. As an important type of non-coding RNA, long non-coding RNA (lncRNA) is closely related to the occurrence and progress of many diseases. The difference in lncRNA expression between the renal papillary tissues of non-calculous patients and the renal papillary tissues of Randall plaque in renal calculous patients suggests that lncRNA may be involved in the formation of Randall plaque. Pseudoxanthoma elasticum is a rare autosomal recessive hereditary disease, caused by a mutation in the ABCC6 gene. Patients with pseudoxanthoma elasticum have a high prevalence of calculi, and plaque formation is observed in the patient\'s kidney, which may suggest that mutation in the ABCC6 gene might be involved in the formation of Randall plaque.
泌尿系统结石具有高发病率和复发率的特点，是泌尿外科的难题。Randall斑块学说是目前学者们普遍认可的肾结石形成机制，Randall斑块形成的理论包括血管钙化学说、成骨转化学说等，目前尚未形成统一的学说。长链非编码RNA作为非编码RNA中一个重要的种类，它的突变或失调与疾病的发生和进展关系密切。与非结石患者肾乳头组织相比，肾结石患者肾乳头钙斑处组织中差异表达的长链非编码RNA提示其参与Randall斑块的形成。弹性纤维性假黄瘤是一种罕见的常染色体隐性遗传性疾病，由ABCC6基因突变所致。弹性纤维性假黄瘤患者有较高的结石发病率且肾内可见斑块形成，ABCC6基因缺陷可能促进Randall斑块的形成。.

OBJECTIVE: To identify the clinical characteristics and pathogenic genes among a Chinese family with angioid streaks and to assess a novel splicing mutation at the transcriptional and translational levels.
METHODS: Consenting family members were clinically evaluated, and blood samples were collected for targeted exome capture sequencing and/or Sanger sequencing. The two affected siblings were assessed by multimodal fundus imaging. ABCC6 splicing patterns were analysed by RNA identification and quantification using the proband\'s peripheral blood mononuclear cells. Minigene experiments were performed to verify the university. Plasmids expressing the transcripts were transfected into HEK293 cells to assess protein translation. Bioinformatic analyses were also performed to predict the splicing patterns and the functional consequences of the mutation.
RESULTS: The two siblings were trans-compound heterozygous pseudoxanthoma elasticum (PXE) patients with the same genotype (c.3703C>T and c.1177-2A>G for ABCC6) but different phenotypes. We identified several ABCC6 alternative splicing transcripts that were not previously reported. The novel splicing mutation c.1177-2A>G led to the upregulation of three transcripts, one using a cryptic splice acceptor in the upstream region of the intron, another using a cryptic splice acceptor in the downstream exon, and the third stimulating non-canonical U12-type splicing. All the transcripts were successfully translated in vitro.
CONCLUSIONS: The genotype-phenotype correlation of PXE is poorly understood. The novel ABCC6 splicing mutation c.1177-2A>G results in multiple splicing patterns. Endogenous U2 to U12 conversion may occur in humans in a disease state. Peripheral blood mononuclear cells can be reliably used to study ABCC6 RNA.