J. de Grouchy

Y ; autosome translocations and mosaicism in the aetiology of 45, X maleness : assignment of fertility factor to distal Yq11

SummaryThree 45,X males have been studied with Y-DNA probes by Southern blotting and in situ hybridization. Southern blotting studies with a panel of mapped Y-DNA probes showed that in all three individuals contiguous portions of the Y chromosome including all of the short arm, the centromere, and part of the euchromatic portion of the long arm were present. The breakpoint was different in each case. The individual with the largest portion (intervals 1–6) is a fertile male belonging to a family in which the translocation is inherited in four generations. The second adult patient, who has intervals 1–5, is an azoospermic, sterile male. These phenotypic findings suggest the existence of a gene involved in spermatogenesis in interval 6 in distal Yq11. The third case, a boy with penoscrotal hypospadias, has intervals 1–4B. In situ hybridization with the pseudoautosomal probe pDP230 and the Y chromosome specific probe pDP105 showed that Y-derived DNA was translocated onto the short arm of a chromosome 15, 14, and 14, respectively. One of the patients was a mosaic for the 14p+ translocation chromosome. Our data and those reported by others suggest the following conclusions based on molecular studies in eight 45,X males: The predominant aetiological factor is Y;autosome translocation observed in seven of the eight cases. As the remaining case was a low-grade mosaic involving a normal Y chromosome, the maleness in all cases was due to the effect of the testis determing factor, TDF. There is preferential involvement of the short arm of an acrocentric chromosome (five out of seven translocations) but other autosomal regions can also be involved. The reason why one of the derivative translocation chromosomes becomes lost may be that it has no centromere.

The 11q;22q translocation: A collaborative study of 20 new cases and analysis of 110 families

SummaryFollowing a previous collaborative study (Fraccaro et al. 1980), 20 new cases of 11q;22q translocation are described. Twelve families were ascertained through an unbalanced carrier of the translocation and eight cases were ascertained as balanced carriers. A segregation analysis was performed on the 110 families so far published. It was concluded that the 11q;22q translocation is a relatively frequent event, and that all the cases thus far reported might have the same breakpoints at 11q23.3 and 22q11.2. The translocation seems to be independent of environmental factors and it seems to have a low rate of mutation as indicated by the scarcity of de novo cases. The new data confirmed that only one type of unbalanced karyotype (47,XX or XY+der(22)t(11;22)(q23.3;q11.2)) is found among the offspring of the translocation carriers. The minimal overall recurrence risk for an unbalanced translocation was estimated to 2%. There was no difference between the recurrence risks for male and female balanced carriers, while the trend was confirmed of an excess of female balanced carriers among the phenotypically normal offspring of the t(11;22) female carriers.

Localisation of the human ABO: Np-1: AK-1 linkage group by regional assignment of AK-1 to 9q34.

SummaryQuantitative red cell adenylate kinase (AK-1) assay has been used in 8 patients with partial duplication or deletion of chromosome 9 in an attempt to find the precise intrachromosomal location of the structural gene locus. All regions of chromosome 9 are represented in abnormal dosage in at least one patient. A 43% increase in AK-1 activity was found to be associated with duplication of the terminal band of the long arm of chromosome 9. Duplication of all other parts of chromosome 9 were associated with normal enzyme activity. These findings not only confirm the assignment of the AK-1 locus to chromosome 9 made previously in somatic cell hybrids, but suggest a more precise assignment to region 9q33→qter. This places the ABO: Np-1: AK-1 linkage group at the distal end of the long arm of chromosome 9.

CHROMOSOMAL AUTORADIOGRAPHY IN THE CRI DU CHAT SYNDROME.

The pattern of DNA synthesis in the chromosomes of Group 4–5 has been analysed in cells from individuals with the cri du chat syndrome. The abnormal chromosome, a No. 5, is one of t

Hypomelanosis of Ito (incontinentia pigmenti achromians) and mosaicism for a microdeletion of 15q1

SummaryHypomelanosis of Ito (incontinentia pigmenti achromians), a sacrococcygeal complex dysembryoma, seizures, severe cerebral lesions, mental retardation, chorioretinal atrophy, hemihypotrophy of the body, and skeletal anomalies are reported in a female infant of North African origin. Karyotype analysis revealed mosaicism for a microdeletion of the proximal region of 15q similar to that observed in Willi-Prader syndrome. The possibility of gene assignment of Itos disease or that it may represent a nonspecific marker for mosaicism are discussed.

Regional mapping of clotting factors VII and X to 13q34. Expression of factor VII through chromosome 8

SummaryBlood clotting factors were investigated in a patient with trisomy 8 mosaicism, a patient with an r(13), and a patient with distal trisomy 13q. Results are compatible with the assignment of the structural genes of factors VII and X to 13q34 and the existence of a regulatory mechanism associated with chromosome 8 controlling the expression of factor VII alone.

Del11p13/nephroblastoma without aniridia.

SummaryA patient is reported with del11p13, low catalase level, nephroblastoma, chordee and cryptorchidism, no evident mental retardation, and with normal irides. This unique observation suggests the following order of loci in 11p13, from centromere to telomere: catalase, Wilms tumor, aniridia. The chromosomal origin of nephroblastoma may be more frequent than estimated on the basis of its association with aniridia.

Aniridia, male pseudohermaphroditism, gonadoblastoma, mental retardation, and del 11p13

SummaryA 20-month-old male patient was referred because of severe growth and mental retardation, bilateral glaucoma, hypospadias, and cryptorchidism. Karyotyping revealed a de novo complex three-chromosome rearrangement as well as deletion of band 11p13:46,XY,t(4;7;15)(q212;p14;q26),del(11) (p13p14). Trabeculectomia revealed bilateral aniridia. Surgery on the genitalia revealed male pseudohermaphroditism and bilateral gonadoblastoma. The kidneys were normal. A deficiency in catalase (CAT) activity allowed the regional assignment of the CAT gene to band 11p13.

Comparison of banding patterns of human chromosomes obtained with heating, fluorescence, and proteolytic digestion

Banding patterns of human chromosomes obtained with various new techniques-quinacrine mustard staining, staining after heating, and staining after proteolytic digestion —are compared. Depending on the

Langer-Giedion syndrome with and without del 8q. Assignment of critical segment to 8q23

SummaryTwo patients with typical Langer-Giedion or trichorhino-phalangeal type II syndrome are reported. One had an apparently normal karyotype. The second had an intercalary del 8q23. Attention is drawn to the severe bone defects seen in the latter and observations from the literature are discussed. The critical segment is assigned to band 8q23. The syndrome may result in a number of cases from a visible deletion, and in other instances from a more conventional gene mutation, although the molecular mechanism is uncertain.