@article {960,
	title = {Expanding the clinical and molecular spectrum of ATP6V1A related metabolic cutis laxa.},
	journal = {J Inherit Metab Dis},
	year = {2020},
	month = {2020 Dec 15},
	abstract = {<p>Several inborn errors of metabolism show cutis laxa as a highly recognizable feature. One group of these metabolic cutis laxa conditions is autosomal recessive cutis laxa type 2 caused by defects in v-ATPase components or the mitochondrial proline cycle. Besides cutis laxa, muscular hypotonia and cardiac abnormalities are hallmarks of autosomal recessive cutis laxa type 2D (ARCL2D) due to pathogenic variants in ATP6V1A encoding subunit A of the v-ATPase. Here, we report on three affected individuals from two families with ARCL2D in whom we performed whole exome and Sanger sequencing. We performed functional studies in fibroblasts from one individual, summarized all known probands{\textquoteright} clinical, molecular, and biochemical features and compared them, also to other metabolic forms of cutis laxa. We identified novel missense and the first nonsense variant strongly affecting ATP6V1A expression. All six ARCL2D affected individuals show equally severe cutis laxa and dysmorphism at birth. While for one no information was available, two died in infancy and three are now adolescents with mild or absent intellectual disability. Muscular weakness, ptosis, contractures, and elevated muscle enzymes indicated a persistent myopathy. In cellular studies, a fragmented Golgi compartment, a delayed Brefeldin A-induced retrograde transport and glycosylation abnormalities were present in fibroblasts from two individuals. This is the second and confirmatory report on pathogenic variants in ATP6V1A as the cause of this extremely rare condition and the first to describe a nonsense allele. Our data highlight the tremendous clinical variability of ATP6V1A related phenotypes even within the same family.</p>},
	issn = {1573-2665},
	doi = {10.1002/jimd.12341},
	author = {Vogt, Guido and El Choubassi, Naji and Herczegfalvi, {\'A}gnes and K{\"o}lbel, Heike and Lekaj, Anja and Schara, Ulrike and Holtgrewe, Manuel and Krause, Sabine and Horvath, Rita and Schuelke, Markus and H{\"u}bner, Christoph and Mundlos, Stefan and Roos, Andreas and Lochm{\"u}ller, Hanns and Karcagi, Veronika and Kornak, Uwe and Fischer-Zirnsak, Bj{\"o}rn}
}
@article {728,
	title = {Pathogenic Variants in GPC4 Cause Keipert Syndrome.},
	journal = {Am J Hum Genet},
	volume = {104},
	year = {2019},
	month = {2019 May 02},
	pages = {914-924},
	abstract = {<p>Glypicans are a family of cell-surface heparan sulfate proteoglycans that regulate growth-factor signaling during development and are thought to play a role in the regulation of morphogenesis. Whole-exome sequencing of the Australian family that defined Keipert syndrome (nasodigitoacoustic syndrome) identified a hemizygous truncating variant in the gene encoding glypican 4 (GPC4). This variant, located in the final exon of GPC4, results in premature termination of the protein 51 amino acid residues prior to the stop codon, and in concomitant loss of functionally important N-linked glycosylation (Asn514) and glycosylphosphatidylinositol (GPI) anchor (Ser529) sites. We subsequently identified seven affected males from five additional kindreds with novel and predicted pathogenic variants in GPC4. Segregation analysis and X-inactivation studies in carrier females provided supportive evidence that the GPC4 variants caused the condition. Furthermore, functional studies of recombinant protein suggested that the truncated proteins p.Gln506 and p.Glu496 were less stable than the wild type. Clinical features of Keipert syndrome included a prominent forehead, a flat midface, hypertelorism, a broad nose, downturned corners of mouth, and digital abnormalities, whereas cognitive impairment and deafness were variable features. Studies of Gpc4 knockout mice showed evidence of the two primary features of Keipert syndrome: craniofacial abnormalities and digital abnormalities. Phylogenetic analysis demonstrated that GPC4 is most closely related to GPC6, which is associated with a bone dysplasia that has a phenotypic overlap with Keipert syndrome. Overall, we have shown that pathogenic variants in GPC4 cause a loss of function that results in Keipert syndrome, making GPC4 the third human glypican to be linked to a genetic syndrome.</p>},
	issn = {1537-6605},
	doi = {10.1016/j.ajhg.2019.02.026},
	author = {Amor, David J and Stephenson, Sarah E M and Mustapha, Mirna and Mensah, Martin A and Ockeloen, Charlotte W and Lee, Wei Shern and Tankard, Rick M and Phelan, Dean G and Shinawi, Marwan and de Brouwer, Arjan P M and Pfundt, Rolph and Dowling, Cari and Toler, Tomi L and Sutton, V Reid and Agolini, Emanuele and Rinelli, Martina and Capolino, Rossella and Martinelli, Diego and Zampino, Giuseppe and Dumi{\'c}, Miroslav and Reardon, William and Shaw-Smith, Charles and Leventer, Richard J and Delatycki, Martin B and Kleefstra, Tjitske and Mundlos, Stefan and Mortier, Geert and Bahlo, Melanie and Allen, Nicola J and Lockhart, Paul J}
}
