Fontaine-Farriaux syndrome: a recognizable craniosynostosis syndrome with nail, skeletal, abdominal, and central nervous system anomalies

Prenatal diagnosis of SLC25A24 Fontaine progeroid syndrome: description of the fetal phenotype, genotype and detection of parental mosaicism

BACKGROUND

Fontaine progeroid syndrome (FPS, OMIM 612289) is a recently identified genetic disorder stemming from pathogenic variants in the SLC25A24 gene, encoding a mitochondrial carrier protein. It encompasses Gorlin-Chaudry-Moss syndrome and Fontaine-Farriaux syndrome, primarily manifesting as craniosynostosis with brachycephaly, distinctive dysmorphic facial features, hypertrichosis, severe prenatal and postnatal growth restriction, limb shortening, and early aging with characteristic skin changes, phalangeal anomalies, and genital malformations.

CASES

All known occurrences of FPS have been postnatally observed until now. Here, we present the first two prenatal cases identified during the second trimester of pregnancy. While affirming the presence of most postnatal abnormalities in prenatal cases, we note the absence of a progeroid appearance in young fetuses. Notably, our reports introduce new phenotypic features like encephalocele and nephromegaly, which were previously unseen postnatally. Moreover, paternal SLC25A24 mosaicism was detected in one case.

CONCLUSIONS

We present the initial two fetal instances of FPS, complemented by thorough phenotypic and genetic assessments. Our findings expand the phenotypical spectrum of FPS, unveiling new fetal phenotypic characteristics. Furthermore, one case underscores a potential novel inheritance pattern in this disorder. Lastly, our observations emphasize the efficacy of exome/genome sequencing in both prenatal and postmortem diagnosis of rare polymalformative syndromes with a normal karyotype and array-based comparative genomic hybridization (CGH).

Bilateral Coronal Synostosis and Mega Cisterna Magna: A Case Report

Craniosynostosis is often associated with raised intracranial pressure (ICP), especially when multiple sutures are involved. In this report, we discuss an unusual association in a patient with craniosynostosis. We report a case of a two-year-old Caucasian male with bilateral coronal synostosis (BCS) who was found to have a concomitant mega cisterna magna (MCM). Although counterintuitive, even in the presence of craniosynostosis, patients with this finding can also have intracranial CSF fluid collections such as the MCM reported here. We hope this report will enhance our understanding of some similar cases that are equivocal regarding raised ICP.

Computational studies of the mitochondrial carrier family SLC25. Present status and future perspectives

The members of the mitochondrial carrier family, also known as solute carrier family 25 (SLC25), are transmembrane proteins involved in the translocation of a plethora of small molecules between the mitochondrial intermembrane space and the matrix. These transporters are characterized by three homologous domains structure and a transport mechanism that involves the transition between different conformations. Mutations in regions critical for these transporters’ function often cause several diseases, given the crucial role of these proteins in the mitochondrial homeostasis. Experimental studies can be problematic in the case of membrane proteins, in particular concerning the characterization of the structure–function relationships. For this reason, computational methods are often applied in order to develop new hypotheses or to support/explain experimental evidence. Here the computational analyses carried out on the SLC25 members are reviewed, describing the main techniques used and the outcome in terms of improved knowledge of the transport mechanism. Potential future applications on this protein family of more recent and advanced in silico methods are also suggested.

Mitochondrial functions and rare diseases

Mitochondria are dynamic cellular organelles responsible for a large variety of biochemical processes as energy transduction, REDOX signaling, the biosynthesis of hormones and vitamins, inflammation or cell death execution. Cell biology studies established that 1158 human genes encode proteins localized to mitochondria, as registered in MITOCARTA. Clinical studies showed that a large number of these mitochondrial proteins can be altered in expression and function through genetic, epigenetic or biochemical mechanisms including the interaction with environmental toxics or iatrogenic medicine. As a result, pathogenic mitochondrial genetic and functional defects participate to the onset and the progression of a growing number of rare diseases. In this review we provide an exhaustive survey of the biochemical, genetic and clinical studies that demonstrated the implication of mitochondrial dysfunction in human rare diseases. We discuss the striking diversity of the symptoms caused by mitochondrial dysfunction and the strategies proposed for mitochondrial therapy, including a survey of ongoing clinical trials.

A 9-year-old Korean girl with Fontaine progeroid syndrome: a case report with further phenotypical delineation and description of clinical course during long-term follow-up

BACKGROUND

Gorlin-Chaudhry-Moss syndrome (GCMS) and Fontaine-Farriaux syndrome (FFS) are extremely rare genetic disorders that share similar clinical manifestations. Because a de novo missense mutation of the solute carrier family 25 member 24 (SLC25A24) gene was suggested to be the common genetic basis of both syndromes, it has been proposed recently that they be integrated into a single disorder under the name of Fontaine progeroid syndrome (FPS).

CASE PRESENTATION

A 9-year-old Korean girl presented with typical clinical features of FPS. She had generalized loose skin with decreased subcutaneous fat, skin wrinkling on the forehead and limbs, skull deformities and a peculiar facial appearance with microphthalmia and midface hypoplasia, anomalies of the digits and nails, a large umbilical hernia and a nearly normal developmental outcome. She exhibited prenatal and postnatal growth retardation together with short stature, and records showed that her height and weight were invariably under - 2.0 SD from birth to the age of 10 years. SLC25A24 analysis revealed a heterozygous mutation reported previously, NM_013386:c.650G > A, p.[Arg217His]. After screening her family for the identified mutation, she was confirmed as being a de novo case of FPS caused by an SLC25A24 mutation.

CONCLUSION

We describe a Korean girl with typical clinical findings of FPS and a de novo mutation in SLC25A24, as well as 10 years of clinical follow-up, including growth and developmental achievements.

De Novo Mutations in SLC25A24 Cause a Disorder Characterized by Early Aging, Bone Dysplasia, Characteristic Face, and Early Demise

A series of simplex cases have been reported under various diagnoses sharing early aging, especially evident in congenitally decreased subcutaneous fat tissue and sparse hair, bone dysplasia of the skull and fingers, a distinctive facial gestalt, and prenatal and postnatal growth retardation. For historical reasons, we suggest naming the entity Fontaine syndrome. Exome sequencing of four unrelated affected individuals showed that all carried the de novo missense variant c.649C>T (p.Arg217Cys) or c.650G>A (p.Arg217His) in SLC25A24, a solute carrier 25 family member coding for calcium-binding mitochondrial carrier protein (SCaMC-1, also known as SLC25A24). SLC25A24 allows an electro-neutral and reversible exchange of ATP-Mg and phosphate between the cytosol and mitochondria, which is required for maintaining optimal adenine nucleotide levels in the mitochondrial matrix. Molecular dynamic simulation studies predict that p.Arg217Cys and p.Arg217His narrow the substrate cavity of the protein and disrupt transporter dynamics. SLC25A24-mutant fibroblasts and cells expressing p.Arg217Cys or p.Arg217His variants showed altered mitochondrial morphology, a decreased proliferation rate, increased mitochondrial membrane potential, and decreased ATP-linked mitochondrial oxygen consumption. The results suggest that the SLC25A24 mutations lead to impaired mitochondrial ATP synthesis and cause hyperpolarization and increased proton leak in association with an impaired energy metabolism. Our findings identify SLC25A24 mutations affecting codon 217 as the underlying genetic cause of human progeroid Fontaine syndrome.

De Novo Mutations in SLC25A24 Cause a Craniosynostosis Syndrome with Hypertrichosis, Progeroid Appearance, and Mitochondrial Dysfunction

Gorlin-Chaudhry-Moss syndrome (GCMS) is a dysmorphic syndrome characterized by coronal craniosynostosis and severe midface hypoplasia, body and facial hypertrichosis, microphthalmia, short stature, and short distal phalanges. Variable lipoatrophy and cutis laxa are the basis for a progeroid appearance. Using exome and genome sequencing, we identified the recurrent de novo mutations c.650G>A (p.Arg217His) and c.649C>T (p.Arg217Cys) in SLC25A24 in five unrelated girls diagnosed with GCMS. Two of the girls had pronounced neonatal progeroid features and were initially diagnosed with Wiedemann-Rautenstrauch syndrome. SLC25A24 encodes a mitochondrial inner membrane ATP-Mg/P_i carrier. In fibroblasts from affected individuals, the mutated SLC25A24 showed normal stability. In contrast to control cells, the probands' cells showed mitochondrial swelling, which was exacerbated upon treatment with hydrogen peroxide (H₂O₂). The same effect was observed after overexpression of the mutant cDNA. Under normal culture conditions, the mitochondrial membrane potential of the probands' fibroblasts was intact, whereas ATP content in the mitochondrial matrix was lower than that in control cells. However, upon H₂O₂ exposure, the membrane potential was significantly elevated in cells harboring the mutated SLC25A24. No reduction of mitochondrial DNA copy number was observed. These findings demonstrate that mitochondrial dysfunction with increased sensitivity to oxidative stress is due to the SLC25A24 mutations. Our results suggest that the SLC25A24 mutations induce a gain of pathological function and link mitochondrial ATP-Mg/P_i transport to the development of skeletal and connective tissue.

Petty syndrome and Fontaine-Farriaux syndrome: Delineation of a single syndrome

In 1990, Petty et al. described two patients representing a novel syndrome with "congenital progeriod" features and neither had classical progeria nor Wiedemann-Rautenstrauch syndrome, though many findings were overlapping. One of the cases had previously been described by Dr. Wiedemann in 1948. The key features of Petty syndrome include pre and postnatal growth restriction, decreased subcutaneous fat with loose skin, enlarged fontanelle with underdeveloped calvarium, coronal synostosis, unruly hair pattern with non-uniform distribution, prominent eyebrows, umbilical hernia, distal digital hypoplasia, and normal or near normal development. Significant overlap to other syndromes, particularly the Fontaine-Farriaux syndrome, is apparent. In 2004, Ardinger postulated that Petty syndrome, like classical progeria, might be secondary to a defect in the lamin A/C (LMNA) gene. The purpose of this paper is to describe two new unrelated cases of this unique syndrome that further delineate the phenotype, compare to phenotypically similar syndromes, and postulate that Petty syndrome could represent a new laminopathy. In addition, evidence suggesting that the Petty syndrome and Fontaine-Farriaux syndromes are variable expressions of the same condition is discussed.