Heterozygous pathogenic variants involving CBFB cause a new skeletal disorder resembling cleidocranial dysplasia

BACKGROUND

Cleidocranial dysplasia (CCD) is a rare skeletal dysplasia with significant clinical variability. Patients with CCD typically present with delayed closure of fontanels and cranial sutures, dental anomalies, clavicular hypoplasia or aplasia and short stature. Runt-related transcription factor 2 (RUNX2) is currently the only known disease-causing gene for CCD, but several studies have suggested locus heterogeneity.

METHODS

The cohort consists of eight subjects from five unrelated families partially identified through GeneMatcher. Exome or genome sequencing was applied and in two subjects the effect of the variant was investigated at RNA level.

RESULTS

In each subject a heterozygous pathogenic variant in CBFB was detected, whereas no genomic alteration involving RUNX2 was found. Three CBFB variants (one splice site alteration, one nonsense variant, one 2 bp duplication) were shown to result in a premature stop codon. A large intragenic deletion was found to delete exon 4, without affecting CBFB expression. The effect of a second splice site variant could not be determined but most likely results in a shortened or absent protein. Affected individuals showed similarities with RUNX2-related CCD, including dental and clavicular abnormalities. Normal stature and neurocognitive problems were however distinguishing features. CBFB encodes the core-binding factor β subunit, which can interact with all RUNX proteins (RUNX1, RUNX2, RUNX3) to form heterodimeric transcription factors. This may explain the phenotypic differences between CBFB-related and RUNX2-related CCD.

CONCLUSION

We confirm the previously suggested locus heterogeneity for CCD by identifying five pathogenic variants in CBFB in a cohort of eight individuals with clinical and radiographic features reminiscent of CCD.

Biochemical analysis of patients with mutations in MTHFD1 and a diagnosis of methylenetetrahydrofolate dehydrogenase 1 deficiency

MTHFD1 is a trifunctional protein containing 10-formyltetrahydrofolate synthetase, 5,10-methenyltetrahydrofolate cyclohydrolase and 5,10-methylenetetrahydrofolate dehydrogenase activities. It is encoded by MTHFD1 and functions in the cytoplasmic folate cycle where it is involved in de novo purine synthesis, synthesis of thymidylate and remethylation of homocysteine to methionine. Since the first reported case of severe combined immunodeficiency resulting from MTHFD1 mutations, seven additional patients ascertained through molecular analysis have been reported with variable phenotypes, including megaloblastic anemia, atypical hemolytic uremic syndrome, hyperhomocysteinemia, microangiopathy, infections and autoimmune diseases. We determined the level of MTHFD1 expression and dehydrogenase specific activity in cell extracts from cultured fibroblasts of three previously reported patients, as well as a patient with megaloblastic anemia and recurrent infections with compound heterozygous MTHFD1 variants that were predicted to be deleterious. MTHFD1 protein expression determined by Western blotting in fibroblast extracts from three of the patients was markedly decreased compared to expression in wild type cells (between 4.8 and 14.3% of mean control values). MTHFD1 expression in the fourth patient was approximately 44% of mean control values. There was no detectable methylenetetrahydrofolate dehydrogenase specific activity in extracts from any of the four patients. This is the first measurement of MTHFD1 function in MTHFD1 deficient patients and confirms the previous molecular diagnoses.

Culture, ethics, and pediatric surgery

This report considers the impact of cultural disparities between patient and physician when the patient is a child and when the physician is a surgeon. The meaning of culture, what an ethics perspective involves, and features of pediatric surgery that are relevant to discussions about culture, ethics, and pediatric surgery are reviewed. Some of the ethical challenges that pediatric surgeons may face when they and their patients have different cultural understandings are explored.

Shifting the autonomy debate to theory as ideology

Some feminists have been critical about the dominant conception of autonomy, questioning, for example, its conception of persons and ideal of personhood. Tom Beauchamp and James Childress (B&C), the major proponents of the dominant conception of autonomy, believe that these feminists have misunderstood their theory and, moreover, that their theory is immune to feminist attack. Their response to feminist critics, however, has been dismissive and does nothing to assuage these critics' concerns. In this paper I briefly review the state of play in this debate about autonomy, showing that B&C are not without positive rejoinders to objections raised by feminist critics. These rejoinders rest on the notion that feminist concerns are a matter of what is logically entailed by B&C's theory of autonomy and attempt to show that feminist commitments are logically consistent with that theory. However, these rejoinders are less than convincing for reasons illuminated by Cheshire Calhoun. Calhoun reminds us that feminists are sensitive to ways in which the shape of discourse is influenced by non-epistemic considerations. In particular, Calhoun draws our attention to the cumulative effect of a whole tradition of moral reasoning that focuses on too narrow a range of moral problems and too narrow an understanding of people and the human condition. B&C's conception of autonomy relies on and reinforces ideologies of the moral life created in just this way. Following Calhoun, I show that criticism of their theory as ideology is not criticism of its logical implications, but something far more damaging, something without available rejoinders.

Preventing and resolving ethical conflicts: more help for policy makers

Institutional policy makers have a useful resource in the "Joint Statement on Preventing and Resolving Ethical Conflicts Involving Healthcare Providers and Persons Receiving Care". Yet, some aspects of the joint statement pose challenges for institutional policy development and merit further reflection. With the aim of clarifying and augmenting the recommendations in the joint statement, this paper gives additional guidance on the issues of benefit, power imbalance, and legitimate decisional authority.