Let me start by reading through the content carefully.
The main topic is about exome sequencing identifying novel mutations in the C5orf42 gene in patients with Joubert syndrome and oral-facial-digital anomalies. The study includes three families.
First, Family 1: Two fetuses from a consanguineous couple in Saudi Arabia. They had multiple anomalies like polydactyly, low-set ears, clubfeet. The first had cleft palate, the second anal atresia. Autopsy showed cerebellar vermis absence, small cerebellum, etc. The mutation found was a homozygous splice-site variant, c.8471-1G4C, which wasn't in existing databases. Both parents were carriers.
Family 2: A 15-year-old female with tongue hamartomas, polydactyly, and cerebellar vermis absence. Her family history includes a sister with a similar condition. Previous genetic testing showed a 3-MB deletion on the X chromosome, but none of the genes in that deletion were linked. They found two compound heterozygous variants in C5orf42. One was previously known, the other novel. The mother had the mutation, but the father's DNA wasn't available. The sister's DNA was degraded, but they think she might have OFD6 with mosaic Turner syndrome.
Family 3: A 1-day-old male infant with a posterior encephalocele, cleft lip/palate, and polydactyly. His sibling died at 5 months with similar features. Exome sequencing found a variant in C5orf42, but the details aren't fully provided here. The study's goal was to expand the mutational spectrum of overlapping features in GLI3-related and OFD syndromes, focusing on polydactyly.
I need to make sure the summary is detailed but concise. Highlight the key findings in each family, the gene involved (C5orf42), the mutations identified, and the implications. Also mention the overlap with Joubert and OFD6, the methods used (exome sequencing, Sanger sequencing), and the significance of the mutations not being in existing databases.
Check for any specific terms or numbers that are important, like the variants, the families, the clinical features, and the autosomal recessive inheritance. Avoid any extra details not in the text. Make sure to mention the autosomal recessive pattern, the key features of Joubert and OFD6, and the conclusion that C5orf42 mutations are associated with these conditions. Also note the study's purpose and the databases checked.
Wait, the user said to start directly with the content, so no introduction. Just the summary. Also, ensure that the language is in English and not add any markers. Keep it factual, mention the three families, the mutations found, the clinical features, and the significance. Maybe end with the conclusion that C5orf42 mutations are a cause for these syndromes.
I need to structure this clearly, maybe in three paragraphs for each family, but the user wants it concise. Perhaps combine the families into a single summary, grouping similar points. Also, note that the study was part of a larger effort to understand the mutational spectrum.
Make sure to include the key features of Joubert syndrome (molar tooth sign, hypotonia, etc.) and OFD6 (tongue hamartomas, etc.). Mention the autosomal recessive inheritance. Also, the fact that the mutations were not found in existing databases, which is important for their novelty.
Check for any other important details: the methods (salting out method for DNA, VarSifter software, Sanger sequencing), the approval by NHGRI, informed consent. But maybe that's too detailed. The user wants a summary, so focus on the main findings and implications.
Avoid any markdown, just plain text. Use clear, concise sentences. Make sure to mention the three novel variants and one previously reported, but the text says three novel and one previously reported in total. Wait, the first paragraph says "three novel variants and one previously reported variant in the C5orf42 gene in patients with OFD6." So in total, four variants, three new. But in Family 1, one variant was found, Family 2 two (one novel, one previously known), and Family 3's variant is not fully described here. Wait, the text says Family 3's exome sequencing identified the variant, but the details are cut off. So maybe just mention that Family 3 had a variant in C5orf42, but the specific details aren't given.
So the summary should state that three novel and one previously reported variant were found in C5orf42 in patients with OFD6. Each family's clinical features and the mutations they had. Also, the significance of these findings in understanding the genetic basis of these overlapping syndromes.
I need to ensure that the summary is accurate, not adding any information beyond the text. Also, check the names of the genes and the OMIM numbers. Make sure to mention the overlap with Joubert syndrome and the key features of both conditions.
Alright, putting it all together now. Start with the study's main point, then each family's details, the mutations found, and the conclusion.
Exome sequencing identified three novel and one previously reported variant in the C5orf42 gene in patients with Joubert syndrome (JBTS) and oral–facial–digital syndrome VI (OFD6). OFD6, a ciliopathy with autosomal recessive inheritance, shares key features with JBTS, including cerebellar vermis absence, the molar tooth sign, and polydactyly. Family 1: Two Saudi Arabian fetuses with consanguineous ancestry exhibited post- and preaxial polydactyly, low-set ears, clubfeet, and cerebellar malformations. Exome sequencing revealed a homozygous splice-site variant (c.8471-1G4C) in C5orf42, absent from databases and controls, with both parents as carriers. Family 2: A 15-year-old female with tongue hamartomas, polydactyly, and cerebellar vermis absence had compound heterozygous variants (c.3599C4T, p.Ala1200Val; c.2920+1G4A) in C5orf42. The c.3599C4T variant was previously described, while c.2920+1G4A was novel. The mother carried the mutation, and the deceased sister likely had OFD6 with mosaic Turner syndrome. Family 3: A Mexican male infant with a posterior encephalocele, cleft lip/palate, and polydactyly had a C5orf42 variant, though specific details were not fully characterized. His sibling, who died at 5 months, showed similar features, including cerebellar vermis absence and hypothalamic hamartoma. The study highlights C5orf42 mutations as a novel genetic cause for overlapping JBTS and OFD6 features, emphasizing their role in complex brain malformations, polydactyly, and other developmental anomalies.
