Parental Narratives About Genetic Testing for Hearing Loss: A One Year Follow Up Study

Few studies examine whether and how parental attitudes towards genetic testing change over time. In this study we interviewed parents of 14 children with newly identified hearing loss at two time points: after referral to genetics and 1 year later. Qualitative analyses of parental narratives indicate that parental attitudes did not change significantly over this time. Parents who perceived genetic testing to be useful continued to value it after testing, while parents who did not perceive it as being useful for their child's future held the same view a year later. The only parents who changed their views regarding the usefulness of genetic testing for hearing loss were those who reported that their children underwent significant changes in their hearing loss or were faced with other life threatening conditions. Parents were also often unaware of the role of the genetic counselor and how genetic counseling could help address many of their lingering questions and concerns. These emergent themes indicate the need for geneticists and genetic counselors to be aware of and sensitized to the questions and attitudes that bring parents to a genetic evaluation, as well as the reasons why parents may not follow up with genetic testing for hearing loss when recommended.

A Patient With Atypical Multiple Sulfatase Deficiency

BACKGROUND

Multiple sulfatase deficiency is an autosomal recessive lysosomal storage disorder characterized by the absence of several sulfatases and resulting from mutations in the gene encoding the human C (alpha)-formylglycine-generating enzyme. There have been a variety of biochemical and clinical presentations reported in this disorder.

PATIENT DESCRIPTION

We present a 4-year-old girl with clinical findings of microcephaly, spondylolisthesis and neurological regression without ichthyosis, coarse facies, and organomegaly.

RESULTS

The child's magnetic resonance imaging demonstrated confluent white matter abnormalities involving the periventricular and deep cerebral white matter with the U-fibers relatively spared. Biochemical testing showing low arylsulfatase A levels were initially thought to be consistent with a diagnosis of metachromatic leukodystrophy. The diagnosis of multiple sulfatase deficiency was pursued when genetic testing for metachromatic leukodystrophy was negative.

CONCLUSION

This child illustrates the clinical heterogeneity of multiple sulfatase deficiency and that this disorder can occur without the classic clinical features.

A male infant with Xq22.2q22.3 duplication containing PLP1 and MID2

Background

The Xq22.2 q23 is a complex genomic region which includes the genes MID2 and PLP1 associated with FG syndrome 5 and Pelizaeus–Merzbacher disease, respectively. There is limited information regarding the clinical outcomes observed in patients with deletions within this region.

Methods

We report on a male infant with intrauterine growth retardation (IUGR) who developed head titubation and spasticity during his postnatal hospital course.

Results

Chromosome microarray revealed a 6.7 Mb interstitial duplication of Xq22.2q22.3. Fluorescence in situ hybridization showed that the patient's mother also possessed the identical duplication in the Xq22.3q22.3 region. Among the 34 OMIM genes in this interval, the duplication of the PLP1 (OMIM# 300401) and MID2 (OMIM# 300204) appears to be the most significant contributors to the patient's clinical features. Mutations and duplications of PLP1 are associated with X‐linked recessive Pelizaeus–Merzbacher disease (PMD). A single case of a Xq22.3 duplication including the MID2 has been reported in boy with features of FG syndrome. However, our patient's clinical features are not consistent with the FG syndrome phenotype.

Conclusion

Our patient's clinical features appear to be influenced by the PLP1 duplication but the clinical effect of other dosage sensitive genes influencing brain development cannot be ruled out.

A recurrent variant in PPP2R5C identified in individuals with macrocephaly, intellectual disability, and seizures

PPP2R5C encodes a B-type regulatory subunit of protein phosphatase 2A (PP2A). This protein serine/threonine phosphatase is a component of multiple signaling pathways and is an established negative regulator of cell division, growth, and proliferation. De novo variants in other subunits of PP2A are associated with neurodevelopment disorders and intellectual disability (ID). We report two unrelated affected individuals with a recurrent variant in PPP2R5C (c.457G>A: p.(Glu153Lys)). Core features in affected individuals include macrocephaly, ID, hypotonia, and seizures. The Glu153 residue is part of a highly conserved acidic loop and directly interacts with the PP2A catalytic subunit. Our results support heterozygous PPP2R5C missense variants as a potential cause of macrocephaly and neurodevelopmental disorder.

DNA-binding affinity and specificity determine the phenotypic diversity in BCL11B-related disorders

BCL11B is a Cys2-His2 zinc-finger (C2H2-ZnF) domain-containing, DNA-binding, transcription factor with established roles in the development of various organs and tissues, primarily the immune and nervous systems. BCL11B germline variants have been associated with a variety of developmental syndromes. However, genotype-phenotype correlations along with pathophysiologic mechanisms of selected variants mostly remain elusive. To dissect these, we performed genotype-phenotype correlations of 92 affected individuals harboring a pathogenic or likely pathogenic BCL11B variant, followed by immune phenotyping, analysis of chromatin immunoprecipitation DNA-sequencing data, dual-luciferase reporter assays, and molecular modeling. These integrative analyses enabled us to define three clinical subtypes of BCL11B-related disorders. It is likely that gene-disruptive BCL11B variants and missense variants affecting zinc-binding cysteine and histidine residues cause mild to moderate neurodevelopmental delay with increased propensity for behavioral and dental anomalies, allergies and asthma, and reduced type 2 innate lymphoid cells. Missense variants within C2H2-ZnF DNA-contacting α helices cause highly variable clinical presentations ranging from multisystem anomalies with demise in the first years of life to late-onset, hyperkinetic movement disorder with poor fine motor skills. Those not in direct DNA contact cause a milder phenotype through reduced, target-specific transcriptional activity. However, missense variants affecting C2H2-ZnFs, DNA binding, and "specificity residues" impair BCL11B transcriptional activity in a target-specific, dominant-negative manner along with aberrant regulation of alternative DNA targets, resulting in more severe and unpredictable clinical outcomes. Taken together, we suggest that the phenotypic severity and variability is largely dependent on the DNA-binding affinity and specificity of altered BCL11B proteins.