Overlapping functions of the cell adhesion molecules Nr-CAM and L1 in cerebellar granule cell development.

The structurally related cell adhesion molecules L1 and Nr-CAM have overlapping expression patterns in cerebellar granule cells. Here we analyzed their involvement in granule cell development using mutant mice. Nr-CAM-deficient cerebellar granule cells failed to extend neurites in vitro on contactin, a known ligand for Nr-CAM expressed in the cerebellum, confirming that these mice are functionally null for Nr-CAM. In vivo, Nr-CAM-null cerebella did not exhibit obvious histological defects, although a mild size reduction of several lobes was observed, most notably lobes IV and V in the vermis. Mice deficient for both L1 and Nr-CAM exhibited severe cerebellar folial defects and a reduction in the thickness of the inner granule cell layer. Additionally, anti-L1 antibodies specifically disrupted survival and maintenance of Nr-CAM-deficient granule cells in cerebellar cultures treated with antibodies. The combined results indicate that Nr-CAM and L1 play a role in cerebellar granule cell development, and suggest that closely related molecules in the L1 family have overlapping functions.

Holoprosencephaly due to mutations in ZIC2: alanine tract expansion mutations may be caused by parental somatic recombination.

We report on the prevalence of mutations in the zinc finger transcription factor gene, ZIC2, in a group of 509 unrelated individuals with isolated holoprosencephaly (HPE) and normal chromosomes. Overall, we encountered 16 HPE patients (from 15 unrelated families) with ZIC2 mutations. Thus, ZIC2 mutation was the apparent cause of HPE in 3-4% of cases. Seven mutations were frameshifts that were predicted to result in loss of function, further supporting the idea that ZIC2 haploinsufficiency can result in HPE. One mutation, an alanine tract expansion which is caused by the expansion of an imperfect trinucleotide repeat, occurred in seven patients from six different families. In three of those families, the father was found to be apparently mosaic for the mutation. We hypothesize that this mutation can arise through errors in somatic recombination, an extremely unusual mutation mechanism. In addition, one mutation resulted in a single amino acid change and one mutation was an in-frame deletion of 12 amino acids. The central nervous system malformations seen in patients with ZIC2 mutations ranged from alobar HPE (most common) to middle interhemispheric fusion defect (one case). Although severe facial anomalies are common in HPE, all of the patients with ZIC2 mutations had relatively normal faces, suggesting that ZIC2 mutations represent a large proportion of HPE cases without facial malformation.

Prenatal diagnosis of a familial Xq deletion in a female fetus: a case report.

X chromosome deletion is an infrequent finding in prenatal diagnosis and presents a difficult counseling challenge when it occurs. We present a case of a familial X chromosome long arm deletion discovered in a routine amniocentesis and subsequently in the mother. The pregnancy resulted in the birth of a normal girl, and X chromosome inactivation skewing was demonstrated in both mother and daughter. Xq deletion phenotypes and counseling issues are reviewed.

Holoprosencephaly due to mutations in ZIC2, a homologue of Drosophila odd-paired.

Holoprosencephaly (HPE) is the most common structural anomaly of the human brain and is one of the anomalies seen in patients with deletions and duplications of chromosome 13. On the basis of molecular analysis of a series of patients with hemizygous deletions of the long arm of chromosome 13, we have defined a discrete region in band 13q32 where deletion leads to major developmental anomalies (the 13q32 deletion syndrome). This approximately 1-Mb region lies between markers D135136 and D13S147. Patients in which this region is deleted usually have major congenital malformations, including brain anomalies such as HPE or exencephaly, and digital anomalies such as absent thumbs. We now report that human ZIC2 maps to this critical deletion region and that heterozygous mutations in ZIC2 are associated with HPE. Haploinsufficiency for ZIC2 is likely to cause the brain malformations seen in 13q deletion patients.

Purification and some characteristics of an oestrogen sulphotransferase from guinea pig adrenal gland and its non-identity with adrenal pregnenolone sulphotransferase.

An oestrogen sulphotransferase, active towards both oestrone and oestradiol, and of high specific activity, is present in cytosol prepared from adrenal glands of both sexes of English Shorthair and Hartley guinea pigs. The ovarian and testicular cytosolic activities of this enzyme are markedly low in comparison with the adrenal activity. The adrenal enzyme is distinct from an accompanying pregnenolone sulphotransferase as judged by f.p.l.c. gel filtration, chromatofocusing, and differences in activation brought about by the addition of thiol groups. The oestrogen sulphotransferase behaved as a 67 kDa protein on a Sephadex G100 column and as a 48 kDa protein on f.p.l.c. gel-filtration columns. Two forms of the enzyme with apparent pI values of 6.1 and 5.5 were eluted during f.p.l.c. chromatofocusing. Sequential salt fractionation, f.p.l.c. gel filtration and elution from an agarose-hexane-adenosine-3',5'-diphosphate affinity gel has resulted in a preparation which, when resubmitted to f.p.l.c. gel filtration, yields a considerably purified oestrogen sulphotransferase. When submitted to SDS/polyacrylamide-gel electrophoresis under reducing conditions, a main protein band of 34-36 kDa is observed. It is suggested that the enzyme may exist as a dimer in the cytosol.